The production number places it within 1968, coincidently matching the model used in the 1968 Bullitt film, where Frank Bullitt (Steve McQueen) carries a Colt Diamondback snubnose revolver as his sidearm.
It's light weight with a good aftermarket grip & a factory target sight. Finished in Colt Blue.
Despite the short barrel it sights reasonably well and is an enjoyable shoot.

