Probably won't help here, but on that G****books site (can't link here due to commercial status) there is US Senate documents for 1892 with lists of names and their trades. There are numerous silversmiths and some engravers. One Francisco Guzman is turning up as a merchant in dry goods and other areas, but not as a silversmith. But maybe he is a retailer? he was in Tehuantepec, Oax.
GoogleBooks...searching Silversmith F. Guzman brought up the documents there, even though he was not one of the silversmiths listed but rather a retail businessman. As far as the eagle stamp associated with the original F. Guzman entry, we are not yet sure what that means but it might link his name to period in Mexican history which could narrow the time frame for searching.