They appear to just be customized factory target "diamond" grips.
The left panel has been cut down to facilitate a speedloader and both have been shortened. What is interesting to me is the wide groove at the bottom of each one. It looks like the person may have liked to shoot with his little finger under the butt, like a lot of SAA shooters do.

I had seen that done to some other grips but don't remember where I saw them.