If the lock was retrofitted, it should be readily evident if you pull the lock and look for evidence. The 5H Mosler/Yale friction fence lock has a unique mounting that would take some effort to mount in place of most locks at the time. I have been told Yale made the locks for Mosler in that era. The 5H uses a spindle mount as pictured and usually has some sort of secondary mount to stabilize it which is sometimes a supporting bracket or bolts through the case. Both of these 5H variations are from Mosler screw door bank safes.
Could the Mosler lock have replaced an original Yale? Possibly, that could be an easy changeover. I am curious about that lock as it has only one bolt going through the lock case. I have not seen one like that. If you take it out please post pictures. What is the number stamped into the wheel pack cover? I can't make it out. I could compare it to my locks as I know the year of my safes, (1891 and 1915)
Is the safe a Mosler? I can't say, but if the serial number is a Mosler one it predates 1886 which is the oldest in the Mosler serial number ledger. While I have never seen a Mosler with that ornate design, who knows what they may have built in the early years. Is the inside intact? Pictures of it may hold clues on who the maker was.
