Stoneware markings generally include the company name, an identifying logo or symbol, and sometimes the mold number, country of origin or artist's initials, which make it possible to identify the value and history of a piece. For example, the marks, "GA. Art Pottery" or "Handmade by W.J. Gordy" indicate Georgia Art Pottery produced from 1935 to 1955. A capital "H" in a circle marks early Hull Pottery; a lower case "h" indicates later pieces.
The Louisville Stoneware company began operation in 1815, but the logo did not appear until 1970. McCoy is a famous name in American stoneware, and its 1905 line, Loy-Nel-Art, includes this name incised in the pottery, sometimes with "McCoy" beneath it.
While these types of markings, usually on the bottoms of pieces, began to become popular in the late 1800s, some producers simply placed the information on slips of paper inserted into the pieces. A surge in patriotism around the time of World War I led to the stamping of stoneware simply with "USA." Identification of pieces that include only "USA" marks or no markings at all starts with the bottom or other unglazed sections of pieces, which show the true colors of the clay and offer clues to the manners of firing. This information and some online resources typically make it possible to identify manufacturers and date stoneware pieces.
Cajun.com, oldantiquepottery.com and artpotterymanufacturers.com are among online resources for identifying stoneware markings.