I've bought and sold at the JDJ auctions. They are just over an hour's drive away, which makes it possible to examine something carefully before bidding. I think Bob's story, above, relates to guns that Turnbull restored. Doug supposedly came and looked them over in person, outed them prior to the auction. There were also some .22rf engraved Winchesters in boxes that weren't factory.
I have no major beefs with JDJ, generally agree with Berien. Like any board regular who thinks he's seen everything, JDJ's folks can be fooled by a really good fake. Most infamous was the "forensically validated" Little Big Horn 1866 - the front cover item - that turned out not to have been there at all. Given the sophisticated efforts employed getting that item so far I cannot lay blame upon JDJ - and they made things right for the buyer, as we'd hoped.
Specifically, when I've asked pointed questions of their experts I've gotten straightforward answers.
Sam