Bottle collecting has become a major American hobby. There are several general categories of bottles, such as historic flasks, bitters, household, and figural. ABM means the bottle was made by an automatic bottle machine after 1903. Pyro is the shortened form of the word pyroglaze, an enameled lettering used on bottles after the mid-1930s. This form of decoration is also called ACL or applied color label. Bottles were first used in ancient China and Rome, often to store liquids. Shapes of bottles often indicate the age of the bottle. For bottle prices from past years, see them listed on Kovels.com/Price-Guide/Bottle.html.