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.This was almost universal with many beverage bottle types (e.g., soda, beer, milk) but was variably common with just about any type bottle - especially prior to 1920.
A substantial amount of bottle type specific information must be reviewed by a user to increase the probability of dating accuracy.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?In addition to technology, products and manufacturers, certain types of glass colors will also aid in dating. This type of bottle was probably dip-molded and dates after circa 1820.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.
Using physical, manufacturing related diagnostic features, most utilitarian bottles can usually only be accurately placed within a date range of 10-15 years (i.e., 1870-1880 or 1885) . Like many industries making the leap from manual craftsman production to industrialization and automation, technological advances in bottle manufacturing were not immediately accepted by glass manufacturers or their workers.