I just recently purchased a used M5906 through Cabelas with a serial number very close to yours. I am curious what the history is on this gun? This is my first day in the forum and I think I am going to enjoy it. The gun looks new inside, mag well is spotless, no wear on the rails, no smell, and dry. I was told by S&W the serial number dates the gun to Mar 1999. It came with a 10 rnd mag, no box or papers. The only unusual part is on the base of the grip towards the rear, in the plastic, there is a small 1/8" hole. Does your gun have this hole too? Anyone have any idea the purpose of this hole on the bottom of the grip? This gun also has a "U" stamped just left of the where the model number is stamped.