The original finish on M1 and M1A1s was a Dulite blue, looks like flat black, but under strong light looks blue, the inside of the receiver looks blue. The barrels were satin-brighter blue. M1 M1A1 Thompsons that were rebuilt were gray-green parkerized. An M1-M1A1 with an original Dulite finish is rare, most all underwent arsenal rebuilds after the war. Most I have seen were in England, after the war they could not afford a rebuild program. Very often some of the acceptance stamps were applied after the finish was applied, if you look close enough. you can see bare metal where the stamp broke the finish. That is a very nice M1A1, I'm surprised it hasn't sold yet, it is priced right.