I was at a show today kicking tires at a table. Guy comes up with an older S&W M&P. Shows it to the table guy. He examines it then hands it back, pointing out that the bottom of the grip has been filed down, removing the serial number. I tell the guy he better be careful, that gun can get him a nice long paid vacation at club fed. Table guy says it's ok long as you dont try to sell it. He checked it again and found what he said was the serial on the back end of the cylinder, really small. Said it would also be on the bottom of the barrel. Said all S&W revos have this. I call BS on this since I checked my S&W's and none of them have this "feature". Opinions?