Numbers (numerals) embossed on the bottoms of glass bottles and jars.
I frequently receive inquiries about what these markings mean. Unfortunately, there is no “one answer fits all” to this question!!
(NOTE: the article on this page is pertaining to GLASS containers, and does not apply to the subject of modern / recent PLASTIC containers, which is an entirely separate field of study, and is discussed on many other websites. The number (within a triangle with rounded corners) found on the bottom of plastic bottles is a code indicating the type of plastic the bottle is made of, and pertains to the subject of recycling) .
Always look very closely over the entire glass bottle or other container to make sure there is not some type of logo (emblem, trademark, initials, or just a letter) that might indicate the actual glass manufacturer. In many cases there is NO such mark, with only a number or numbers to be seen. In these cases, the general style, shape, glass color and other characteristics can at least help narrow down the possible age range of a particular specimen.
A large percentage of bottles are marked with only a number (or numbers) on the base (or the heel), and the truth is that (in most cases) it is very difficult, or impossible, to assign a specific glass manufacturer to a bottle if there is no other information embossed in the glass.
Probably in the majority of cases, single digit numbers are mold numbers, merely serving to identify a particular mold, (or section/mold cavity in an automatic bottle manufacturing machine) that was used to form the bottle or other glass item. If a number of identical bottle molds are being used simultaneously, each mold would be assigned a number. (If problems occur with the finished product, it can be easily ascertained which mold or mold section is at fault.)
Numbers also serve other purposes, depending on the exact container and/or company being discussed. Some numbers are year/date codes. Some numbers (for instance, 3- or 4-digit numbers on the base of many British bottles) are catalog, inventory, style or design numbers assigned to a particular bottle shape. Those numbers would serve to identify a particular bottle style, such as in communications/orders between the glass manufacturer and their customers …….that is, the companies who ordered the bottles to package their products.
Many Owens-Illinois Glass Company soda bottles, for a period of time, used “G-numbers” on the bottom (numerals before or after a G), which were codes for a specific bottle shape (design), irrespective of the soda brand name or glass color.
Many whiskey bottles are seen with “D-numbers” on the bottom which (correct me if this is wrong) have to do with distillery information.
Date codes are often seen, especially on soda bottles from the 1930s to date, and many of these codes are embossed on the base of the bottle, placed to the right of the glassmaker’s logo. This is true on the products of some manufacturers, but not all.
Most modern glass bottles carry date codes, which are often on the heel of the bottle. These date codes are not always obvious, or easy to distinguish from bottle mold numbers. It also depends on exactly which glass company produced the container, as all firms do not use the same system of markings.
DOTS or BUMPS around the lower heel of bottles.
In many cases (especially within just the last few years, writing this as of 2013), mold data information is now preserved through the use of small embossed “dots”, “bumps” or raised periods arranged horizontally around the lower heel of the container. More information on this invention (which is rather involved!) and how it works can be found by doing an internet search (Google, Bing, Yahoo or other search engine), using the keyword search terms “EP 0256804 B1 ” , “code reader”, and “Emhart”.
Please click here to return to the Glass Bottle Marks pages. (This link points to page three).