I went to the Post Falls gunshow today and saw a really interesting old M&P that the seller said was from 1940
The cool thing about it was that it had a very unusual length barrel - around 3". The roll marks were perfectly centered and the rollmark on the left side of the barrel had a dingbat character at each end - I can't recall if it was a caliber marking or a S&W rollmark, but I recall noticing the dingbat characters. The thin part of the original sight blade had been cut off, and a slot milled in the remaining base for a pinned sight blade with a brass bead to be installed in the slot. The slotted base looked like an original forged part of the barrel - not something soldered on or added later. Judging by that and the crown of the barrel, it sure didn't look as if it had been cut.
The left side also looked like it had been refinished at some point in the distant past - because the logo rollmark looked shallow and washed out, as did the barrel roll marks. There was no address line on the right side - maybe polished off? I'm thinking it was possibly refinished at the same time that the sight blade was replaced.
The $500 price tag seemed pretty ridiculous to me, but the real deal killer was the butt.
The lanyard ring hole was drilled right through the serial number - which by the spacing of the remaining numbers appeared to be a 5-digit number with no letter prefix. I even talked the guy into letting me remove the grips to see if the serial number had been re-stamped on the side of the grip frame. It hadn't.
So basically a BATF illegal and prohibited gun.