I acquired a DAO M64-5 sometime back and just noticed that the hammer and trigger are both case hardened. Is that the usual, or are stainless more appropiate? The sn is : CBS 3362, about '97 I think. It came with rubber Hogues. I was hoping to find some sign of NYPD, but nothing. On right side of grip, on the butt is electroetched "21512" space and "764". What is the meaning of these numbers?