Facsimilies

My use of auction catalog illustrations has the big advantage in that if you turn them over you can immediately see they are copies; no need to write anything on the back. Also they look much better than the stuff being sold on ebay. Some of those are terrible. One seller has dozens of listings, his copies are all faded and wouldn't fool a novice. There is a guy in Latvia selling US facsimiles- his copies of the bank note issues are the wrong size.
I recall once buying an ebay lot purporting to be a copy of a complete set of plates of the GB penny black. When they arrived they were tiny, about half the stamp size and the reproduction was so poor you couldn't pick out any details. That seller had positives from several buyers of them and seemed puzzled as to why I returned them!