Our first example to the right (Exhibit D), fortunately for me, is extremely easy to determine the date of production.
Since 2063 has yet to pass, and the company did not exist in 1863 nor did it use that symbol prior to the 1950's, the only possible year of production is 1963. I am unsure of whether or not this particular example follows the general trend of date code to the right of the symbol. If we assume that the 7 is indicative of a year, it could mean anything from 1957 to 2007.
The plant code is of no use either to help narrow down the date.
The number 17 is for a plant in Clarion, Pennsylvania which has been in operation since 1932 and is still presently producing bottles.
In 1941, the United States of America formally entered World War II on both the Pacific and European fronts.
Resources became limited as many industries focused on manufacturing supplies to support the war effort.
As a conservation measure during the war, the amount of glass used for many bottle types was reduced. The number in that picture could either be a 6 for the plant code, meaning it was made in Charleston, West Virginia, a plant that was in operation from 1930 - 1963 (Society for Historical Archaeology) or it could be a year code of 9. They axed the diamond, and instead were left with a simple I inside of an O (see pictures to the right and below).
You can't really tell from the picture, but the green glass in Exhibit C is quite thick, thicker than anything we would see today, which leads me to believe that the glass was indeed manufactured in 1939, and has been sitting in the creek ever since, waiting for me to find it. If it is a year code, the thickness of the glass and the lack of a period after the 9 suggests a manufacturing date of 1939. The general trend, however, remained the same with the plant code on the left of the symbol, and a date code to the right.
Now, I know from the use of the symbol on the glass that both pieces pre-date the mid-1950s, but is there a way to narrow that down? The general rule when dating glass with the O-I symbol is the number to the left of the symbol is the plant code, and to the right of the symbol lies the date code.
Other numbers, such as the 7 in Exhibit C, are specific to the production plant, and letters, such as the A in Exhibit E, usually stand for the glass model (e.g.
What first led me down this path of discovery was a small piece of glass I found washed up on my local creek with the word “where the surface of the hot, just produced bottles, were sprayed on the body, shoulder, and neck (not base or the top of the finish) with a stannic chloride (Tin (IV) chloride) vapor that allowed the tin to bond to the outer surface providing scratch resistance and durability to the bottles." (Lindsey, B.) Though this process is still in use today, the word was embossed on bottles only between 1940 and the mid-1950s (Lindsey, B).
Therefore the piece of glass I found was manufactured using this process somewhere in that time frame.
If you are an avid beach glass collector, or a collector of glass bottles, jars, cups, etc, you may have noticed an odd symbol and/or numbers on your find and didn't know what they meant. Usually, the symbols are a logo for a company, and the numbers a code for where and when the particular glass item was produced.