I'd say you're right about that Rory. It doesn't look perfectly straight across at the back. I see a tiny curve to it, unless the camera is doing that. Must have been a last minute act of desperation. BTDT...
Looking at it again the top does appear to be slightly curved, but that is from a beveled edge that gets deeper at the sides, so it's just at the top edge - possible from what's left of an even bevel on a curved back? but I see no signs of any curved machining, all the machining lines behind the locking surface are perpendicular to the bolt.
The serial number is 84550, which I though was not very close to the change to the rounded rear bolt, but Rory informed me that right around that number is when they made the changes and jumped to 90,000 leaving a gap in the numbers, so it's near the change over point. I had thought the bolt was possibly a later replacement, but seeing the condition of all the other internal parts match, I now think it could be original to the gun. With how little wear is on the internals that had to be a very nice gun before they customized it. I have no idea who did the work, or when.
I will look into the Galazan product, the lacquer seems to work, just not real smooth, but I think I know what caused that, I sprayed it outside and it was at the low end of the temperature range listed on the can. It's just going to sit for now, getting rid of that chromed lever has been something I've wanted to do since I got it.