Instructions
Determine if the antique purple pitcher is made from transparent or opaque glass. Some glassware manufacturers produced transparent colored glassware as well as opaque ceramic-type glassware. More often than not, genuine antique glassware will have a maker's identifying mark on the base of each piece. The lack of a mark could be an indication of a fake, a replica or a mass-produced piece that was used as a promotional item for various businesses. Many Depression glassware patterns were used as promotional items or sold very cheap to make them more accessible to average Americans. Since a lot of Depression glass was mass-produced, manufacturers did not always include a maker's mark with their patterns.
Familiarize yourself with glassware manufacturers from the 1800s and early 1900s. Eliminate makers that did not produce any type of purple glass, as some manufacturers only produced a certain number of colors in their glassware. Consult with online sources and antique glassware books at the local library or bookstore. Concentrate on the sources that offer lots of pictures which will make it easier to identify an antique purple pitcher with no markings. Ebay can be a useful resource for identifying antique glassware through pictorial examples.
Examine your antique purple pitcher for a pattern. Often times, an antique glassware piece that is missing a maker's mark---common with many examples of Carnival glass---can be identified by its distinct pattern. "Florences Glassware Pattern Identification Guide" by Gene and Cathy Florence contains hundreds of glassware patterns shown in detail for easier identification. At patternglass.com you can find Pattern Glass School which provides descriptions and photos of various glass patterns.
Expand your search by visiting antique shops and shows and by talking with local antique dealers who can often recognize a particular glassware pattern. They may also be able to offer additional informational resources. Peruse retail websites such as RubyLane.com or the collectorsdream.net which exhibit pictures and descriptions of authentic antique glassware examples.