Instructions
You can tell if your item is pre- or post-1930 merely by looking at it. Jugs and stone crocks are pre-1930. Kitchen items began in the 1930s. Muggsy ceramic comic strip gift items were created in the 1940s. Dinnerware also began in the 1940s.
Look at the back of the piece for distinguishing marks. Various "keystones," such as an engraving or stamping in the stoneware, were used in different production periods. Early pieces are marked "Pfaltzgraff Stoneware co. LTD York Penna." In the 1930s, a large "P" and "YORK" were used. In the 1960s, a keystone of the Pfaltzgraff family castle appeared on the back of the company's pieces.
If you are looking at a piece of dinnerware, certain names can be clues to age. Gourmet Oven Ware and Provincial Gourmet appeared in the 1940s and '50s. Heritage, the oldest pattern of dinnerware still in production, was introduced in 1963. The Yorktowne pattern began production in 1967.