My 64-5 is / was a Phoenix police exchange. With ~150,000 64's traded in across the country, there's going to be umteen mixed names, ID scratches and stampings over the entire lot.
Glock has done the same with their 19's and 22's. My 22 is from the Fulton County Ga. correctional system. Interesting to guess their history and most were only shot during qualifying. Never have had a problem with trade-ins.