Dating an antique bottle
Lettering on the body will give clues to the contents and lettering on the base will give clues to the manufacturer. Is the bottle machine made and aqua- or light green in color? For example, glassblowers still make hand-blown bottles today.
Both require more specific research to refine the bottle's date beyond observation of technology. Aqua glass typically dates from the late 19th century to the 1920s. Bottles with a purplish or amethyst hue are made from manganese dioxide glass and date circa 1880 to 1920. Also keep in mind that bottles could have been used and refilled multiple times.
Do the mold seams go all the way from the base to the lip?
This is a machine-made bottle and dates after 1910. This will be shallower, wider and more perfectly circular than a pontil mark.
A pontil rod held the nearly molten bottle during the final stages of manufacture.
The scar was left when the pontil was detached from the bottle. If the seams disappear in the neck, the bottle was probably "blown-in-mold" and dates circa 1820 to early 1900s.
By the mid-19th century, embossed lettering and marking on bottle bodies and bases, denoting manufacturers and products, made more precise dating possible. Is the bottle highly symmetrical, but lacking mold seams?
The information on this website will, however, usually produce a reliable manufacturing date range for a majority of American utilitarian bottles manufactured from the early 1800s to the mid-20th century.But any technique, once developed, can be used right up to the present - as many collectors know who have been so unfortunate as to rely too heavily on a popular termination date as sure evidence of true antiquity..." (Toulouse 1969b).In short, there was (and is) nothing to stop a glassmaker from using an obsolete method in the production of a bottle.3.Check for lack of bubbles and uniform glass thickness.This is another indication of a machine-made bottle. Most bottles with embossed lettering date from the late 19th century and later. Keep in mind that older technology often persisted and some bottles date later than you might think.