Listed here are the trademarks or logos of the major U.S. cast iron hollow ware-producing foundries of the late 19th and early to mid-20th centuries.
Trademarks varied from as simple as the name of the city of manufacture in plain, block letters, such as the coveted "Erie" pieces produced by Griswold in the late 1800s, to the more elaborately-styled scripts, logos, symbols, and descriptive markings used by Wagner, Griswold, Martin, Favorite, and others up through the 1950s.
1Heat Ring "Erie" Skillets
2Heat Ring "EPU" Skillets
3Smooth Bottom "EPU" Skillets. The slant logo made an encore appearance on a handful of skillet sizes after the introduction of smooth-bottomed pans, before being replaced by the small block logo.
4The large block logo is seen shrunken to accommodate size restrictions such as on small skillets or the undersides of lids. It is also seen in slightly varying diameters on pieces of the same pattern number, leading some to differentiate smaller instances as being a "medium logo". The term "large", however, is more properly applied to the block lettering rather than the diameter.
5During its period of production, the small block logo skillets underwent design changes to the handles, resulting in what are known as the early, late, and late grooved handles. The early handles are dated ca. 1939-1944. At what points the changes thereafter occured is uncertain.
6The medium block logo or late large TM is believed to have been a planned replacement for the small block logo, but whose development was possibly cut short by the acquisition of Griswold by Wagner Ware. Information dating it to as early as 1955 has been found.
8Pieces so-marked appear to be from Wagner Sidney O. patterns modified to add the word "Ware" to the trademark.
9This contradicts published sources placing the "pie logo" much earlier, as early as 1915. No pie logo skillet, however, is known without a 4-digit catalog number, which is presumed to have been first used by Wagner ca. 1924. And, with the exception of a few very large sizes, pie logo skillets are of the smooth bottom design generally dated from after 1930.
All date ranges are best estimates of when a particular TM was produced, and do not necessarily denote the beginning and/or end of production of that TM. Production of many makers' different trademarks often overlapped by several years.
The warmer the temperature of a lye bath, the faster it works to remove build-up from cast iron pans.