Vintage Doubles does a good job. So does Champlin. I know Tom Bryant at Cabela's has made an effort to get the Gun Library people to post photos of barrel flats on their website. Sometimes successful, sometimes not. Mark Beasland has been putting more of his inventory on Guns International, and he's giving you pretty much everything you want. I'm always surprised that even some dealers who specialize in doubles don't include a lot of information informed buyers would like to know.