Neil, Welcome to the Forum. On unusual Randall Knives I'm sure that Rhett, Rick and most of the other folks here would agree that if you are in the market to sell, eBay is most likely to bring you the greatest exposure and therefore the highest prices. Most of us here will sell on eBay for exactly that reason. If two or more collectors have a hankering for the same knife, there's no telling what might happen. It's a little different for the more "standard" Randalls, but even then we (the folks who post here) are sometimes mighty surprised and how much a nice Randall sells for.
Regards, Doug