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runscott1) look at loads of ebay auction scans. You can be sure that cards being sold by reputable dealers (Mike Wheat, etc.) are real, so use those as your "benchmarks".
2) once you feel "comfortable" that you know what a t206 should look like, buy a few "beater" commons on ebay from a reputable dealer,i.e: cards that there is no incentive to reprint.
3) study them intensely - all you need is your eyeballs and a 10x.
end result: if you ever get a reprint, you'll know it. T206's are not brain surgery.