Thank you David. I agree that it is a complicated subject. The barrel address in your second photo matches the barrel address on my 22" featherweight barrel that I mentioned in my original post. (I recently had that barrel properly fitted to a 1919, Style 2, .250-3000.)
With respect to the later barrels, I have a 1931 99K that came with a .410 barrel. My impression from the seller was that the barrel had been with the rifle since new. At any rate, it indexes perfectly, and both barrels have Style 8 barrel addresses. (Sorry, the .410 barrel isn't for sale!)
