I know the nature of selling guns can send a shivver down a spine ... and an examiner may look at it a little deeper ... but if it is a legitimate company, they are regulated with extreme scrutiny. I don't consider them any higher than any other business, as long as there are no other red flags (similar to other businesses) ... example - if they only sold guns online, I may take an extra peek.
Dealers in Firearms and/or ammunition must have a Federal Firearms Dealer License. My dad, who did industrial engraving, had to get this license to even have the gun frames in his shop to engrave the caliber,serial numbers, manufacturer etc. for the manufacturer. This could be checked to verify the legitimacy of the dealer. It could possibly be another piece of CIP documentation in this case. The Bureau of Alcohol, Tobacco and Firearms is where you would probably start. They are pretty serious about these.