There are specialized publications with ads for firearms auctions. "Shotgun News" is one; there is a website as well as sales at the major chain bookstores. (Others here might know of more publications.) It might be that you could get some information by emailing your pictures to one or more of the auction companies.
Your rifles are in a far more specialized and limited collector's market than what most of us know about...
You're from BATFE? Come right in! I use all your fine products!