A lot of gun makers didn't make their own locks. Sometimes different makes of guns would have the same lock. Clean it up a little to see what we can see.
Model 1861 Springfield or one of the private contractors licensed to make the 1861. No way to know for sure who the maker is without seeing the markings on the plate, they were made to be exact and interchangeable with the Springfield. Odds are it is a Springfield made one, just because of the numbers produced.