I ask for ukara and check that the letters at the start are actually for a site, that much you can do on their website. The second check is to get their forum name and the date on some paper in a picture of rifs that they already own and arn't two tone. Just as evidence that they must (I assume/hope) have got at least some of them from a retailer and by proxy, be a skirmisher.
Not full proof. But it feels like I did what I could. Though in all honesty, I only really press for it on profiles that are clearly new, or just not really used (no postings/reviews) and clearly only popping on here for the classifieds.