$1500 is probably in the ballpark for the patriarch of the Mountain Gun, sans box and goodies; one in nice shape is getting harder to find, they only made 5000 of them. The 629-2 Mountain Revolver came with Pachmayr Grippers, so those may be the originals.
I have one remaining complete 629-2 and wouldn't sell the package for less than $2K+, if that.
Here's a little history lesson on the Mountain Revolver and it's offspring