Instructions
Check the bottom of the bottle for any marks or writing. If it has remnants of a paper label you may be able to determine the maker or the contents of the bottle.
Inspect the design of the bottle. C.W. Robacks stomach bitters bottles had circular ribs that went around the bottle. The sour mash figural barrel bottle of 1867 also had circular ribs, but they were wider and there were fewer of them. This bottle may have the name Chapin and Gore on the bottom or on the label. Manufacturers used olive and amber colors in making these bottles.
Count the number of ribs on the bottle and notice whether they are circular or vertical. There were several varieties of bitters bottles and flasks. The Pitkin flask can have 32 or 36 ribs in green or olive green color. There was also a 12-rib clear glass flask. The English produced a 36-rib flask in an olive yellow color. Pitkin flasks are either green or olive green colors with a broken swirl pattern.
Fill the bottle or flask you are trying to identify with water, then pour it into a measuring cup. Do not fill it all the way to the top, leave about 1 inch head space. This will help you determine how many ounces the bottle held. You can then state the correct size of the bottle.