I do not believe Roper or Sanderson put medallions in their grips. At least I've not seen any. Furthermore, I've never seen a pair of factory grips with those arrow-head pointers.
On early I-frame extension stocks, that area was just a point, not an arrow-head. Also, I've never seen any zebra-wood stocks attributed to Roper or Sanderson, although Sanderson did work with exotic woods.

I have no knowledge of who might have made these, but it wouldn't hurt to ask Keith Brown if he has any ideas.

Regards, Mike Priwer