Biggi; On the left side of the frame is UO over Z in a shield outline, about 1/4" high, in the upper left corner. I don't think the grips are original to the gun, when they are removed, the engraving continues behind the grips. The aluminum back strap looks like it might be an after thought. The serial # is 5946 & the rear sight is stamped with the same 46.       Thanks again,,,,,,,...MIKE...