My collecting lesson was simply "Don't buy anything in a category that you know absolutely nothing about." About 9 or 10 years ago I purchased a handful of "Civil War era" dental instruments which I intended to research, place in a shadow box, and give as a gift to my daughter in law who is a young, practicing dentist. She does appreciate history! One of the items, a bone handled tool of some type, had indeed been authenticated by the seller (who I knew to be trustworthy). He had NOT researched the other instruments, but I figured that with one authentic tool of the era with a value of about $80 to $120, it would be worth the gamble for me to get the other instruments in a package deal, research them myself, and go for it at a total price of something like $160. Bad Decision - I could not identify some of the instruments within 10-15 years, and two of the instruments were from the 1940-1955 timeframe and were of practically no value. Fortunately, the seller was willing to give me a Store Credit equal to the amount that I had paid him, which I gladly accepted and used for some known items. Whew!