These appear to be a rather cheesy foreign made grip that has been sold heavily on Ebay and the gun auctions.
These have some sort of medallions, but often they turn out to only look like Colt medallions until you get a close look.
There are a number of grips available for the Diamondback.
After 1966 all Colt "D" frame revolvers like the Diamondback, Detective Special, Cobra, and Agent used the same "stubby" grip frame. All grips for these will interchange.
Among the grips available for the Diamondback are Hogue Mono-Grips in fancy wood, and with or without finger grooves:
You send them a tracing of your hand and they custom fit grips to you.