RC - couple of things. The horseshoe nail thing was very likely done, although I've heard several versions. There would have been no special properties imparted. But, they were a good source of salvage steel.

I'd bet on the gunsmiths' demise from "tuberculosis" was actually silicosis from grinding barrels. Brit barrel makers had the same problem.

Sorry, but I don't know any details on Bis. Lot of good stuff here. Keep it up!!