Better pictures, or a name on the barrel or lock, would make for an easier answer.
Could be French or English, etc. 1750 would be a good date guess, but could be 50 years later too.
The wood carving looks nice although not unusually fancy, and it looks like a little bit of simple engraving on the metal. Despite the nice looking carving, this wouldn't have been a high end pistol of the time, more of a mid range example.
Price-wise, I think it would sell for $1500/$2000 tops and probably less. If it was made by a famous maker, maybe a bit more.
The broken hammer could be repaired pretty easily for a couple hundred bucks or so. Tell your friend not to loose the broken piece of hammer because having to make a replacement part would up the repair bill by a good bit!
John
