I suppose it's down to me to make sure I'm as informed as I need to be. The main thing, as a coin dealer with a reputation to keep I really can't afford to get involved with areas I know little about. Or at least I shouldn't try to sell coins about which i know nothing about. For example, I once bought a large amount of coins from a woman who's dead dad used to be a coin dealer. I was pushed for time and I went through what she had quite briefly and paid her some money and left. I got the coins back home and among them was an ancient Greek coin, an expensive one at that if it were real, but I wasn't sure, so I didn't try to sell it, just locked it away in a box. On my next visit to the UK I thought i'd see if I could arrange to see here again, as there were things I remembered and probably could have looked at more thoroughly. I went back, bought mostly scrap silver and left overs. Among the left overs was an ancient Greek coin, exactly the same shape, weigh, die alignment, size etc as the one I got on the first visit! Impossible to get 2 absolutely identical ancient Greek coins....... Both fakes of course. So, in short, I simply don't sell what I don't know.