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 (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 ……is, the companies who ordered the bottles to package their products.The base of a bottle typically only has one primary function (besides helping hold the bottle together) and that is to provide a flat surface for the bottle to stand upright.Of course there are exceptions to that "rule", most notable being the rounded base mineral & soda water bottles whose purpose was to make sure the bottle did Bottle bottoms aren't flat because they need an arched structure to allow them to be stable on a flat surface.This list primarily includes marks that represent the actual glass company that made the container.
Prior to 1890, laws dictated that bottle could not be bottled at the brewery. Sanitation was a problem, especially since the product was not bottled at the location it was made.This potential for datable features is very useful since bottles are more often than not lacking embossing - an attribute which can often enhance dating opportunities.Also, shape is extremely variable and usually only loosely connected with age and function.(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) .