Like the idea! Sure there are plenty of negative tales of unscrupulous dealers, but also plenty of stories of great buys by learned collectors!
Years ago I was wandering through an antique market looking for interesting military antiques and came across what the dealer claimed was a Rev War English Dragoon pistol, the only problem being that it was one of the notorious copies built in Japan post WW2. As my wife pulled me along I noticed in the same glass case what appeared to be an old miniature portrait of a soldier in armor. The dealer was so intent on trying to sell me the flintlock and gain a big sale that he downplayed the miniature as an old little painting he had picked up as part of a bigger lot in Europe years previous. I told him my suspicions about the gun, and he seemed legitimately surprised. I then examined and bought the miniature. Now I don't collect art, but because of my interest and research in the Thirty Years War I recognized the small portrait as that of Christian the Younger (or "The Mad" according to Catholic propaganda at the time), who was a famous Protestant military leader early in the war. The portrait looked to be oil on copper which I remembered as one of the styles of the early 17th century, and the frame was covered in old wormholes and looked period. The portrait wasn't much and worth the risk, and turned out to be a genuine period portrait of the Protestant hero. Upon further examination I even found an old collection label on the back of the copper dating to the early 1900's. Now I am not saying the portrait is a five figure lottery winning, but it turned out to be a truly historical piece worth a lot more than I paid, and it became a welcome addition to my fledgling collection of Thirty Years War militaria, all because I initially took interest in a fake flintlock.
I would love to hear stories of other great buys on your part!