I wonder if that was SOP throughout the production life of the Krag. Two sight bases I had cause to remove over the years were simply soft soldered on and popped right off with heat from a propane torch. Also, they weren't dovetails, but rather a simple flat milled into the barrel on which the sight base sits square. The original carbine barrel I have sitting in front of me right now is like that, and it's one I popped the sight base off of a couple weeks ago with propane, the remaining solder is definitely lead based- it scrapes off with a dull pocket knife. (It's going onto my Krag sporter I'm building.) I have no reason to believe it had ever been messed with.