That's a tough one - don't know if that question has ever come up before. Barrel steel alloys have been the normal topic of conversation and research but not the steel used in the frame. The frame was drop-forged and then shaped and machined from the forged block. All machining and engraving was done to the frame and then charcoal case hardening was the last thing done before the final fitting. Don't know if any kind of special alloy was necessary but many of the internal parts were of special alloys and hardened as well where wear would have been a factor.
