Photos are the best way to ID cast iron pans. There are some often seen with a number inside a diamond shape at the 6 o'clock position, and typically a letter to the right of it. There are others with a letter in the diamond I have seen which look very much like the number in diamond ones. The answer in the case of those is either late Favorite or Chicago Hardware Foundry, who bought Favorite's tooling and patterns when the went bust.