With the double-bump prawl at the top, the wide flare at the base, and the "P" in the model number/code, I'd guess Colt Python.
Or you could call/email Herrett's Stocks and ask them:
I didn't see that model code in their current listings, but I might have missed it. Looks like they have a lot of possible combos when you include checkering options and such. EDIT: They might be the Roper model for the Python, with optional fine-line checkering (that would explain the "RP" model designation).