My dad just bought a S&W M64-8 yesterday from a local shop. He was told that the revolver was a trade in from some LE agency but we don't know what agency it might be. The revolver is in great condition with the exception that "TR-4" is scratched/poorly electro-penciled into the sideplate and the frame under the cylinder on the left side and the shop owner told us that all the revolvers from that contract had been similarly marked except for one. Does anyone know what agency this revolver might have come from? I'm guessing it's most likely a prison system as prisons are the only LE agencies I know of still using revolvers in large numbers at such a late date (the -8, from what I can tell, was introduced in 2004), but any input would be appreciated.