The thing that I find a little suspect is that in the trade thread there is no mention of him having more than the 2 pictured for trade. So he listed 2 items for trade and then traded those 2 items many times. I don't know about everyone else but that doesn't sit right with me.
That doesn't sit right with me either since it indicates that you suspected the legitimacy of the items, but traded anyways.
Innocent until proven guilty?
I'm still giving time for responses before I pass my own judgement.
That said, you have to admit that it can easily come across as shady and that those actions do seem to indicate that they knew something was probably off. Think of it this way, if a well known, collected, and desirable artist produced a series of lithographs or giclées where only 5 of them were done and someone managed to get 5 of them years after release in a matter of weeks or from one person, wouldn't that be suspicious? And if you saw someone selling 5, wouldn't you question the authenticity? And furthermore, if you decided to sell or trade them, but only listed one of them for sale or trade, wouldn't that further reinforce the notion that you knew, or at the very least, suspected the integrity of the work?
I'm not casting stones because there could very well be more underlying this and there could be actual ignorance that caused this issue, but you do have to acknowledge how things could be seen another way.