A few years back, I was asked to conduct the analysis of a fairly large assemblage of amber bottle glass that was excavated by the University of Texas at El Paso. Most of the artifacts were fragmentary and consisted of amber beer bottle glass. This provided me the opportunity to observe a large sample of amber beer bottle bases from the 1933-1941 period. I noticed an interesting pattern in the Owens-Illinois bases that did not fit the description from Toulouse's Bottle Makers and Their Marks. That set me on a quest to look at as many Owens-Illinois bottles as I could find (mostly beer, soda, and milk) to see if the pattern occurred regularly. What I discovered was a more refined way to date Owens-Illinois bottles from the 1940-1946 period with information provided by their marks. While I was looking, I discovered that Pepsi-Cola bottles made by Owens-Illinois followed a still different pattern in their markings as did those from Coca-Cola.
The Owens-Illinois Glass Co. began with the merger of two of the industry's giants: the Illinois Glass Co. and the Owens Glass Co. The Illinois Glass Co. was incorporated in March 1873 and began business in August. The company was successful and made virtually every type of bottle. By 1911, Illinois Glass had obtained the first of three Owens Automatic Bottle Machine licenses and made many other containers from semiautomatic machines. The firm expanded until the merger with Owens (see Lockhart et al. 2005a for a discussion of the company and its marks).
The Owens Bottle Co. (1911-1929) grew from a series of companies that began with the Toledo Glass Co. (1896-1903). The Toledo company was succeeded by both the Owens Bottle Machine Co. (1903-1911) that made and sold the Owens Automatic Bottle Machine and the Northwestern Ohio Bottle Co. (1904-1908), a company that make bottles. In 1929, the firm merged with one of its major competitors, the Illinois Glass Co. to form the largest glass company in the industry.
The merger between the Owens Glass Co. and the Illinois Glass Co. brought under the Owens umbrella the "largest individual bottle plant in the world" (Paquette 1994:71). The merger was formally approved on April 17, 1929 (Paquette 1994:70). On March 25, 1931, the firm was incorporated in California as the Owens-Illinois Glass Co., Ltd. The newly renamed organization purchased the Illinois Pacific Coast Co., the largest glass manufacturer on the West Coast on November 30 of the same year. The name of the West Coast operation was changed to the Owens-Illinois Pacific Coast Co. on April 23, 1932 (Paquette 1994:81-82). According to Paquette (1994:81) Owens-Illinois introduced Applied Color Lettering (ACL) in 1931, although other sources place the date of the practical application at 1934. Owens-Illinois purchased Brockway, Inc. in 1988, renaming the combined giant Owens-Brockway. According to Paquette (1994:45), the Owens scars appeared on the earliest bottles, made in 1904 and 1905 and continued until the final two machines, "AQ" models, were phased out of the Gas City, Indiana, plant on December 17, 1982.
There are at least three different types of marks embossed on returnable bottles by the manufacturer. These were probably not placed on the containers at the behest of the purchaser (the actual bottler) but reflect the needs of the glass house. The first type is the manufacturer's mark. These are usually symbols and/or letters embossed on the heel or base of the bottle that identify the maker of the container. These were used at least as early as 1821 by Henry Ricketts on his now well-known style of mold that included what was probably the first plate mold (often called slug plates - although the industry term was "plates") on the base of his bottles.
Date codes are usually one- or two-digit numerals that indicate the year the bottle was made. This idea appears to have been conceived in conjunction with machinemade bottles. At this point, I have not seen date codes embossed on any blown-inmold bottles (with the possible exception of Hutchinson bottles made by the Illinois Glass Co. between 1901 and 1903). Date codes are often integral with manufacturer's marks, embedded in mold codes, or they stand alone. They probably originated as tracking devices for returnable bottles. Manufacturers and bottlers alike wanted to know the number of round trips a bottle would make in typical use.
Mold codes are cryptic marks embossed on the heels or bases of bottles. According to Miller and Jorgensen (1986), "bottle mould [a "u" in the word mold is correct in British and Canadian English] numbers serve several functions," including the following:
Although Miller and Jorgensen provided a thorough understanding of the marks from Dominion Glass Co., we have little evidence for the meanings of mold codes from most companies. In some cases these codes identify the individual plants that produced the bottles. Mostly, we have little or no information about the meaning of mold codes.
Often, these "mold codes" are synonymous with numbers in the company catalogs. Thus, I have begun calling these specific types of mold codes - catalog codes. The glass group to which I belong has successfully matched numerous codes found on bottles with illustrations in the Whitall Tatum and Illinois Glass Co. catalogs. In other cases, we have been able to match numerical codes on numerous identical bottles to empirically define codes by certain companies (e.g. Illinois Pacific Glass Co.) as catalog codes.
Paquette (1994:87-88) discussed the creation of a code system at the end of Prohibition (1933):
At the outset, the need was for standard sizes, shapes and capacities. And [Smith L. Reardon] said, "The Secretary had the idea that the government needed to know that bottles would not be refilled and would be tamper-proof. So each of the distilleries [received] an identifying number and my proposal was that each of the bottle factories also be numbered.
After several weeks of study and discussion, a simple code was devised. Numbers were used to identify the month and year the bottle was manufactured and the plant in which it was made. An appropriate logotype or symbol would be added to identify the glass company which produced the bottle.
The Diamond OI Mark
As Reardon's discussion shows, sometimes all three types of markings are combined. The Owens-Illinois Glass Co. marks provide a good example. A letter from Toulouse to May Jones, published in Volume 5 of The Bottle Trail (1965), was the first to identify (at least in print) the relationships between the Owens-Illinois mark and the numbers surrounding it. Toulouse (1971:406) later explained in more detail that the Owens-Illinois manufacturer's mark also contained additional information in the form of company, date, and mold codes. The trade mark is an I inside an oval (or an "O" for Owens) superimposed on an elongated diamond (the traditional mark of the Illinois Glass Co. - the combined logo sometimes called the diamond IO mark). The mark (#269,225) was registered on April 1, 1930, and the company claimed first use on April 20, 1929 (Creswick 1987:154). To the left of the mark is a one- or twodigit number that identifies the plant that produced the bottle. Toulouse provided a table on page 395 (Table 1) that identified all the Owens-Illinois plant codes. To the right of the mark is a one- or two-digit date code, and a mold code (also numerals) appears below the mark.
Both archaeologists and collectors, however, have been perplexed that the single- digit date codes could reflect either the 1930s or 1940s. For example, a date code of 2 could indicate 1932 or 1942. In some cases, other ways of dating the container (such as the presence of an Applied Color Label - a technique not perfected until 1934) could determine the decade of manufacture.
According to Toulouse, however, bottle production apparently began in 1930, so that eliminates the question of whether a single 9 would indicate 1929 or 1939. While looking at the amber beer bases from the El Paso excavation, I noticed an interesting change in bottles marked with a zero (0). The site was the old distribution center for Grand Prize Beer, and the Grand Prize Distributing Co. occupied the site from 1939 to 1943. Because Prohibition was not lifted until 1933, this meant that bottles marked with a zero were probably from 1940. However, many of the bottles had a zero followed by a period. These also had embossed stippling (in the form of numerous tiny dots) on the bases. All bases marked 1. or 2. also had stippling, and none of them were missing periods. As noted by Toulouse (1971:403), the Duraglas (script) mark first appeared in 1940. Creswick (1987:155) noted that the block-lettered Duraglas trademark (#384,993) was registered on February 11, 1941, but was first used on September 4, 1940. Owens-Illinois registered the script version of the mark (#390,467) on September 23, 1941, claiming first use on September 4, 1940. On beer bottles, the Duraglas mark was consistently used in conjunction with stippling. The reason for stippling is not intuitively obvious. According to the GlassPac Web page (2004):
During the manufacture of a glass container there is a point at which the almost red hot bottle is lowered on to a relatively cool conveyor. Glass is a poor conductor of heat. Therefore on contact with metal, the surface of the glass will cool quickly but the mass of glass behind it will not, leaving a temperature differential in the glass setting up stresses which may cause microscopic cracks to appear that may weaken the glass. Base stippling lifts the body of the bottle clear from the conveyors restricting the heat loss from the bottle and eliminating the possibility of stress and possible weakness.
|Plant Number||Plant Location||Dates of Operation|
|2||Fairmont, West Virginia||1930-present +|
|3||Huntington, West Virginia||1930-present +|
|4||Clarksburg, West Virginia||1930-1944|
|6||Charleston, West Virginia||1930-1963|
|7||Alton, Illinois||1930-present +|
|8||Glassboro, New Jersey||1930-1939|
|9||Streator, Illinois||1930-present +|
|12||Gas City, Indiana||1930-present +|
|13||Chicago Heights, Illinois||1930-1940|
|14||Bridgeton, New Jersey||1930-present +|
|17||Clarion, Pennsylvania||1932-present +|
|25||Terre Haute, Indiana||1934-1950|
|15**||Waco, Texas||1938-present +|
|20**||Oakland, California||1946-present +|
|23||Los Angeles, California||1949-present +|
|10**||Atlanta, Georgia||1960-present +|
|21||Portland, Oregon||1960-present +|
|4**||Rockport, New York||1962-present +|
|8**||New Orleans, Louisiana||1962-present +|
|22||Tracy, California||1962-present +|
|11**||North Bergen, New Jersey||1963-present +|
|5**||Charlotte, Michigan||1968-present +|
|16**||Lakeland, Florida||1967-present +|
* All dates are approximate; Toulouse used a graph that was not precise.
In a personal communication, Robert C. Leavitt added, "At least some of the dot coding on the bases of modern bottles is for Q C [quality control], to identify the cavity on a machine that produced a specific bottle. If too many bottles fail QC, they know where to look."
Subsequent observation revealed that the combination of one-digit numbers and periods were to be found on soda and milk bottles as well. Eventually, a pattern emerged with the following results. At some point in 1940, someone in the Owens Illinois Glass Co. seems to have realized that a zero could indicate either 1930 or 1940, so a new code needed to be developed. The answer was to add a period indicating a manufacture of 1940 or later. The stippling idea appears to have evolved about the same time, and all this was conceived in conjunction with the Duraglas process. Owens-Illinois continued the singledigit numeral/period system until 1946, although the company began integrating a two-digit system as early as 1943, but the 43 date code is rare. That means 1940s bottles may have either a 0 or 0. marking, but 1941 and 1942 are almost always marked 1. or 2. Occasionally, these periods are difficult to see because they are concealed in the stippling, but periods are generally larger than the stippling dots. Bottles made in 1943-1946 may contain either single-digit numerals followed by periods or doubledigit markings, such as a 4. or 44 for 1944 (figure 1).
In several cases, the initial 4 has been added as an afterthought, frequently slightly out of alignment with the other digits associated with the logo. Occasionally, a mold engraver forgot to change the code. The initial bottle used by the Illinois Brewing Co. of Socorro, New Mexico, for example, was made in 1946 and has a single 6 to the right of the Owens-Illinois manufacturer's mark but with no period after the number. However, I have found few exceptions to the period rule on returnable bottles. By 1947, the change to double-digit date codes appears to have been completely adopted by all the plants.
Even though the Owens-Illinois engravers changed the date code each year, they did not create a new baseplate each time. On many Owens-Illinois bottles, it is fairly easy with minor magnification to discern tooling marks where the old date code was peened flat and a new one imprinted into the mold to appear as an embossed date. By the 1960s, the changes are virtually impossible to detect, probably because of improved technical skills.
Peening out old marks seems to have been used pretty extensively. Mike Miller discovered an interesting colorless, soft drink bottle embossed "21 I-in-an-oval-superimposed- on-an-elongated-diamond 7" on the front heel. This mark was used by the Owens-Illinois Pacific Coast Co. (a subsidiary of Owens-Illinois) from 1930 to ca. 1954. The back heel, however, is marked 1 followed by a blanked-out triangle. The Owens-Illinois workers used an old mold from either the Illinois Pacific Glass Corp. or the Illinois Pacific Coast Co. (both predecessors to the Owens-Illinois Coast Co. and both users of the triangle logo) to make the bottle. The 7 to the right of the Owens-Illinois mark is a date code for 1937 (the final year the plant was open), so the mold had laid in storage at least seven years prior to its reuse. To remove all doubts, the factory code 21 is for one of the two San Francisco (former Illinois Pacific) plants.
The bottom number on the logo also requires a bit of discussion. Toulouse (1971:403) noted that the bottom number indicated "mold details." However, Paquette (1994:87-88) stated that after Prohibition "a simple code was devised. Numbers were used to identify the month and year the bottle was manufactured and the plant in which it was made. An appropriate logotype would be added to identify the glass company which produced the bottle." The timing of this is off. Both the Illinois Glass Co. and Owens Glass Co. used logos to identify their products prior to the merger that created Owens-Illinois in 1929. The new company adopted a logo and began marking its bottles with the plant code (left of the logo) and the year code (to the right) immediately.
I tested the "month code hypothesis" with the few bottles I had handy. I found numbers of 1, 2, 5, 7, 8, 14, 16, and 18 (although the 14 was on the later style of logo - without the diamond). The 14, 16, and 18, therefore, could not be codes for the month. Toulouse was apparently correct about this one. However, the bottom number was applied inconsistently. Although many bottles from the early 1930s include the bottom number, a large segment of them do not. Even as late as the 1950s, these numbers are sometimes missing.
Owens-Illinois changed to a new variation of its manufacturer's mark during the mid-1950s. The new mark was identical to the old one except that the elongated diamond was eliminated leaving only an I in an oval. The dating scheme, however, remained the same with the company code to the left of the mark and the date code to the right. Other combinations of letters and numbers often appeared on some part of the base, possibly identification numbers for the bottle style (catalog numbers), although they could have other meanings. The timing of the change is subject to a bit of controversy. According to Toulouse (1971:403), the older mark (with diamond) was used from 1929 to 1954, and the new mark (without the diamond) was used "since 1954." Peterson (1968:49) agreed with a beginning date of 1954 for the new mark. Both almost certainly referred to the change that occurred in 1954. Although planning for the change had begun a year earlier, 1954 was the year that Owens-Illinois Glass Co. became Owens-Illinois, Inc. The conversion included a modification of the logo to the "'I' placed within a larger 'O'" (or oval). It was not until shareholders voted at the company's annual meeting on April 21, 1965, however, that the name was legally changed (Paquette 1994:147). As you will see below, the transition was not nearly as smooth as the official pronouncement would indicate.
Using empirical methods, Giarde (1980:80), discovered that the "diamond and circle mark appears on milk bottles through 1956 with the new circle mark appearing on 1957 milk bottles." Giarde's ideas set me looking through my soda bottles, and I discovered the older diamond-oval-I marks
Figure 1. Owens-Illnois Mark, 1944 Example
with date codes up to 58 (1958) and David Whitten found one from 1959 (from factory #7)! Although currently unconfirmed, a date code of 60 (1960) in conjunction with the older mark has been reported. The newer, I-in-an-oval marks, however, began at least as early as 1956 (a 56 date code), so there was a minimum of a three-year overlap. If we could find enough bottles with both types of marks from 1954 through 1958, it would be interesting to see which factories changed at which times. It may be that some plants adopted the new system earlier than others. The Oval I mark continued in use after the 1988 name change to Owens-Brockway and is still used in 2005 (Powell 1990; Emhart 1996:49; 2005).
Owens-Illinois was very inconsistent with its date codes. My "key" holds true most of the time, but neither it nor any other will be 100% accurate. The dot system was used on returnable bottles from 1940 to at least 1946. The earliest two-digit code I have heard of or seen was 43 (1943). Occasionally (especially on whiskey bottles), the code to the right of the logo does not make sense as a date code and should be ignored. Other times, the plant and date codes are placed somewhere else - not in conjunction with the logo. On many flasks, the factory and date codes are both to the left of the logo (separated by a dash) and are oriented perpendicular to the logo. More empirical and historical research needs to be undertaken on liquor-bottle codes, and Carol Serr is currently collecting such data.
As a slight aside, Giarde (1980:77-94) devoted 17 pages to discussion about the Owens-Illinois Glass Co. Along with specifics about dating, he included a section on the lightweight milk bottles (invented by Julian Harrison Toulouse), tables about the dates on the lightweight bottles, discussions about each individual plant, and a section on coffee creamers. Giarde is by far the best reference for manufacturer's marks on milk bottles.
Owens-Illinois also used the older mark (with the diamond) in three slightly different variations. All three differences center around the I inside the diamond. The first is a simple vertical line (sans serif lettering). The second style has two horizontal bars, one attached to the top and one to the bottom of the "I" (serifs). The final style has the serifs but they are slightly upswept and attached to the oval (figure 2). At this point, I have not been able to find a specific connection between factories or time periods. These seem to have been used at the whim of the engraver rather than as identifying marks from factories. The newer mark appears in the first two styles but not the one with the serifs attached to the oval. In some cases, especially on smaller bottles, the "I" is reduced to a dot.
An interesting exception to the usual markings is the date (and plant) codes on the bases of Coca-Cola and Pepsi-Cola bottles. The two major soft drink companies (Coke and Pepsi) have both required bottle makers to adhere to specific requirements in marking their respective bottles. For a good survey of manufacturer's marks, date codes, and other information associated with Coke bottles, see the Coke Bottle Checklist (1996) by Bill Porter. Porter discussed where date codes and other marks are found and what to look for. Lockhart (2000; 2003:34-37) consolidated known data on dating the characteristics of Coca-Cola bottles.
Figure 2. Owens-Illinois Variations
Before making a connection with Owens- Illinois, a few generalizations about manufacturer's marks on Coca-Cola bottles need to be examined. The earliest variation of the almost universally known "hobbleskirt" bottle is marked PAT'D November 16, 1915. Many of these have no manufacturer's marks. When such marks are present, they are usually on the heel of the bottle. Until 1934, the bottles made by Owens- Illinois maintained the standard Owens- Illinois marking system (e.g. 9 OI mark 3) located on the heel. Virtually all glass houses making Coke bottles had changed to "skirt" markings by 1934 (see below). This consists of a two-digit mold code followed by a manufacturer's mark (in the case of Owens-Illinois, the earliest mark with the elongated diamond) and the twodigit date code (to the right) all embossed on the narrowest constriction of the "skirt" or lower half of the bottle. In 1951, two changes occurred simultaneously. The date code migrated to the left, and the manufacturer's mark moved to the base of the bottle. The remaining embossing on the skirt was the two-digit date code, a dash (-), then the two-digit mold code on the right. These changes occurred about mid-year, so Coke bottles are found with both configurations. Some Owens-Illinois-made Coke bottles actually used the standard Owens- Illinois format (e.g., 24 OI mark 4 - Porter 1996:4, 7).
The Owens-Illinois mark on Coke bottles changed to the Oval-I mark about 1954 (when it changed on other bottles - see above). The final mark-related change on Coke bottles occurred by at least 1953 (probably in 1951), when Owens-Illinois began placing a smaller single letter above the manufacturer's mark to identify the plant making the bottle. Factories and marks included A (Alton, Illinois); B (Bridgeton, New Jersey); C (Charlotte, Michigan); F (Fairmount, West Virginia); S (Streator, Illinois); and W (Waco, Texas) (Porter 1996:4).
I have seen no comparable work on Pepsi bottles, so I include my observations here (although Stoddard's most recent book  contains much helpful dating and historical information). Prior to Pepsi's adaptation of Applied Color Label bottles (often called painted-label bottles or pyroglazing, in the case of milk bottles), the company did not require any special coding, so all early bottles are marked just like any other bottle from the respective glass companies. However, beginning with the first ACL fountain syrup bottle in 1943, all Pepsi bottles followed a specific format. Although I will use the Owens-Illinois marks as examples, the same basic format applies to other companies as well (although the earliest bottles followed the older formats). On Pepsi bases, a line of numerals and a single letter appears above the logo. The first one or two digits is an unknown code that may indicate the area of the country (the only one I have seen in New Mexico and El Paso, Texas, is 14) followed by a single letter (all I have seen so far are either A or B) followed by a two-digit date code.
Generally, another single-digit number will appear to the left of the logo, and a singleor double-digit number will be placed at the right (figure 3). The right-hand number is often (but not always) identical to the date code or to the last digit of the date code. Also, either above or below the logo and the line of code above it is a single letter followed by a three- or four-digit number. This is probably a mold code, although the meaning is currently unknown.
Figure 3. Pepsi-Cola Owens-Illinois Mark, 1944 Example.
From looking at El Paso soda bottles, it appears that plants 9 and 6 were the most active in making soda bottles with the older logo (1929-1959) (although soda bottles were also made at plants 3, 18, 19, and 23). Plants 5, 7, 9, 15, and 20 made soda bottles with the newer logo (after 1955). Oddly, Toulouse (1971:403) claimed that "there were no plants 5 and 19." However, those numbers appear (with highly legible embossing) on El Paso soda bottles. Two different bottles bearing the I-in-an-ovalsuperimposed- on-an-elongated-diamond manufacturer's mark bear a "19" in the space to the left of the logo. Similarly, one container with the later I-in-an-oval mark shows a distinct "5" to the left of the logo. It is clear that Toulouse was confused about plant #5. In his table (Toulouse 1971:395; reproduced here as table 1), he lists plant #5 in Charlotte, Michigan, which opened about 1963. Although he calls it an "old number reassigned," it is likely a new plant number that was skipped earlier. In a table provided to David Whitten by a representative from Owens-Illinois, however, factory #19 is listed as being in Crenshaw, Pennsylvania. The table also included factory numbers as high as 52! Obviously, Toulouse only listed the earlier plants.
Owens-Illinois also manufactured fruit jars. Creswick (1987:107-108) lists several jars made by Owens-Illinois and its Pacific Coast subsidiaries. Jars were embossed on the reverse heel MANUFACTURED BY OWENS-ILLINOIS GLASS CO. or MFD. BY OWENS ILLINOIS GLASS CO. or MANUFACTURED BY OWENS-ILLINOIS GLASS COMPANY. One misstrike read MANUFACTUPED BY OWENS-ILLINOIS GLASS COMPANY. Subsequent evidence suggests that jars and bottles bearing the full name of the company were manufactured for export. Such containers are found as far away as New Zealand - embossed on the bodies with local company names (Lockhart et al. 2005b).
In a personal communication, Mike Elling noted that ca. 1944-1945 (World War II) Owens-Illinois seems to have run short of red pigment. Mike has a Royal Crown pyramid bottle that is missing the red that was typically used on the label. Billy Grice offered a yellow-only Squirt bottle on eBay with a 1945 Owens-Illinois mark and date code embossed on the base. He stated that "during the war many west coast bottlers went to single colors." It is probable that red dye was in short supply during the end of World War II. Owens-Illinois may have only experienced the shortage for the final year or so of the war.
One additional discrepancy is worth mentioning. In very small bottles, Owens- Illinois often left off the date, plant, and mold codes completely; only the logo remained. Another exception was provided by David Whitten. He sent information on several pharmaceutical bottles with OI logos and dated paper labels, one of which had the OI logo (no diamond) but only had a single-digit date code. The date code (5) matched the prescription date of 11/23/55. Apparently, on small (but not tiny) bottles, the company reverted to a single-digit date code to save space. David also has several more small bottles with the OI logo and a single-digit date code. The abbreviated date code was apparently pretty common on small bottles.
A final discrepancy was also noted by Whitten (personal communication). This concerned a slight difference in the Owens- Illinois logo during the 1930s. The marks tended to be "taller and larger, and the oval is maybe a bit more 'squared' or 'vertically rectangular' at least . . . compared with later ones." By the 1940s, however, marks became more refined and smaller. This trend toward reduction in line thickness and increased clarity of the mark and codes continued into the 1980s.
Owens scars, found on the bases of all bottles made by an Owens Automatic Bottle Machine, are discussed in numerous publications (e.g. Jones & Sullivan 1989:37- 38). These scars are caused by the suction process of drawing the glass into the mold, a technique that is unique to bottles made by the Owens machine (on bottles made in the U.S.). As the glass was sucked into the mold, it was sheared of by a "knife." This shearing action created the scar. These are often described as "feathered" or "rough," but that does not accurately describe all Owens scars. Although we currently have no documented evidence, empirical observation suggests that this feathering may have been caused by dull knives. Over time, the feathering decreases until most Owens scars consist of only a single line. Probably, technicians learned to change or sharpen the knives more frequently or some other technical discovery allowed for the more refined scar.
On later bottles from the Owens company, for example, the scars consist of a roughly circular fine line. Usually, this line is debossed or sunken into the glass (unlike embossing and most mold lines which protrude from the glass surface). However, the Owens scar may be raised above the surface of the bottle.
The Owens scar is rarely centered on the base. It is often so off center that it extends over the heel and onto the body of the bottle. This is especially true of smaller bottles, but the phenomenon also occurs on fairly large containers.
Thus, we find that the Owens-Illinois coding system is a bit more complex and revealing than we originally thought. The transition period between one- and twodigit date codes is usually clearly marked. This research confirms Toulouse's date of 1940 for the use of the Duraglas mark and also sets a date (1940) for the use of stippling on bottle bases by Owens-Illinois. In addition, Pepsi-Cola and Coca-Cola required a slightly different date coding, and date codes were either eliminated or abbreviated on some smaller bottles. Owens-Illinois, however, was very inconsistent with its coding.
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