Ha! I've got this one.
May, 1968, bitchezzzz... The same year and month that the NYPD launched the famed SOU and started taking requests from store owners.
That would make the hot set up a 4" heavy barrel M10 S&W loaded with Lee Juras' 110-grain SWCJHP Super-Vels doing 1,125 out of the M10 (per Jim Cirillo from his GB&G book). I'm sure there was other awesome out there, but hard to argue with the date line up, the SOU, and someone like Mr. Cirillo.