I saw a 30-40 Trapdoor once, I think it was in a TX museum.  Interesting rear sight the mauser has, with that double notch when down, looks like there might be some limited windage adjustment.  The 30-40 on the mauser barrel appears to me to have been stamped on later, maybe by the fellow who liberated it from the Armory?  I've seen a few rifles over the years that might have walked out of Springfield's collection.