Saw a bunch lot of countefeits uploaded to omnicoin and I had to write something about it. The so called expert challenged me to explain why they are counterfeit. I'll refrain from giving exact words but I found it hilarious. http://omnicoin.com/collection/Yeyong If you reckon any of those "crowns" are genuine, I would like to know. These are actually very easy to tell.
I recommend you not tell them anything about how you know their coins are counterfeit. . . that simply informs them of where they need to put more effort into perfecting their craft.
It's interesting the quality range of these. At the low end you have that well known 1882 8 reales, and then at the opposite end the Trade dollars and Indo-China piastre which are very convincing. Some of them I can see why a collector would get fooled, but find it hard to believe they don't see why at least a few of them are undoubtedly fake. A few of these you can tell from across the room. Also, the weights of the coins are included in the pictures, and many of them are way off. I think this person may just be trolling