Posted By:
drcRelevant to the original post, the below linked booklet goes through all the methods and theory of card dot/printing patterns, ink, paper stock, etc.
http://cgi.ebay.com/Early-Baseball-Cards-Authenticity-Guide-Booklet_W0QQitemZ8809862438
As the author of the booklet, I agree with others that if a collector avidly collects T206s (or 1933 Goudeys or 1971 Topps), almost all reprints will be obvious, as they simply won't look right.
Knowledge of modern verus old printing patterns and such is important when the collector is looking at an issue he is unfamiliar with.