When you are able to take clear photos we can give you a better idea of its value, hard to tell from the photos from the seller.
If the former owner can't find the "factory letter", here is a link to request one:
Smith & Wesson Historical Foundation - Letter Process - Insuring that the rich history of Smith & Wesson will continue for generations to come
Again, it is difficult to tell any details about the gun, but if it happens to letter as an engraved New Model 3 it may be worth more than suspected. Understand perfectly if you don't want to disclose what you paid for it
.