Gipper: Welcome to the forum! As Headknocker mentioned, I have a Model 042 just like yours. It's still NIB, has the same high-polish finish, and shows no sign of an overstamp:
I recently picked up a second one, also NIB, but this time it was the matte-finish version, and it has a very clear overstamp--"MOD. 042" over the previously-stamped "MOD 642". It also came with Uncle Mike's boot grips, while my polished version was equipped with Uncle Mike's combat grips. (Sorry, no pics of the matte 042 yet.)
A letter from Roy Jinks, the Smith & Wesson factory historian, mentions that the 042 was made in 1992 and 1993 using Model 642 frames that were rejected for cosmetic reasons (difficulty matching the natural aluminum finish to stainless steel). The frames were anodized in a black finish, and were fitted with blued carbon steel barrels and cylinders, plus stainless steel yokes finished in midnight black. Total production of the 042 was 4415 guns.
You're right about the original Model 42 having a grip safety, but I don't think it was a mistake that S&W gave this newer model essentially the same number. They've been known to re-use model numbers from time to time, sometimes even for guns that bear no resemblance to one another. In this case the gun was virtually identical to the old Model 42 except for the grip safety, and since the 042 was never a cataloged model--just a special run to use up the rejected 642 frames--the factory probably decided to use that number just long enough to get them out the door.
A good article with more info on the 042 can be found
HERE.
Congrats on owning a great revolver!