I have a model 10-7 with a 5 inch barrel chambered in .38 special. Serial number 4D17207. The backstrap is marked Detroit Police 21618. It's also nickel plated. Is there any way to confirm that this gun was ever used by the Detroit Police department? I know the model 10 used to be as common as a Glock is today in police holsters. Local gun store guy said he had not seen a nickel plated duty weapon before. I don't know much about S&W's and any help would be greatly appreciated.