In the case where we see ghost marks of a foundry other than the one who made the pan or a design that is an obvious copy, there are two possibilities. One is that the producing foundry purchased used patterns from another foundry. In the case of Erie ghosts on Wapak skillets, it seems highly unlikely that Griswold would have given a competitor such a generous helping hand, even if the patterns were obsolete to them. We also know from pieces containing ghosts of their own obsolete marks that makers updated patterns, so obsolete patterns obviously still held value to their original owners. The other, more plausible scenario is that the producing foundry side-stepped the most expensive part of the pattern making process by using another actual pan in some way to create working patterns of their own.