Lol, what is some sort of an authenticity card?
Joking aside, I would stay the heck away. Whenever a website is overzealous about the authenticity of its items, especially one like this, it is never a good sign. Why would a reputable site state that its respective owners are aware of authenticity issues but that you should trust them? It just screams fishy to me.
Also, the previous poster with only 2 posts stating that she loves this site and it met the positive reviews she read on it is a little concerning. A Google search yielded no such positive reviews that I could see...