I can't remember the exact year, but after I moved from fitting the Mod 52's I moved to assembling the 39's 59's and 41's. I was chosen to assemble the first of the production 645's. Loved that guns size, basically like a big 39. I always wondered why they used a phillips screw for the ambi-safety, ugliest part of the gun. If you look at the bottom of the frame around the mag well, a fitters stamp would be there. If it's an "0" that's one of mine.