Here's where it gets confusing...
Your 629-2 is a "Mountain Revolver", not a "Mountain Gun". The difference? Laser etching on the barrel that says "Mountain Gun".
The Mountain Revolver was the first issue of this species by *&* as a limited run special.
Response was overwhelming. Folks went gaga over the things.
You could sell them new for more than retail.
*&* saw a good thing, and decided this item might need to make a more regular showing; hence, the "Mountain Guns". So they do a batch of 'em every so often; .44 Mag in '93, '94, and '99, as well as .45 Colt in '96.