I believe, based on my limited research, you are correct about the 2M stamp... only field guns had that stamp... so it was strange that my father's gun had the 2M and was new in the box... must have been on the shelf waiting for issue when the switch happened and just got sent back to S&W and then sent to distributors... not complaining, just surprised my father got lucky enough to land one... I was with him at the gun show when he got it... along with our parish priest that bought his first centerfire revolver, a model 19 snubby... maybe there was a higher power at work...hmmm... you know that "mysterious ways" thing...