One of the most interesting things about T206 was the random way it was produced and distributed. There were spurts. A lot more is known now than there was say, 40 years ago. A lot of what Topps has done in the past two decades, with parallels, short prints, etc., were inspired by this very set. One important thing I look for is the color registration. I'll give you an example below. If you can spot the differences and notice one face is much clearer than the other, this is the type of stuff you want to be patient and seek out. These cards were meant to be state-of-the art color pictures, so if you see any cards that display that level of clarity these are the ones you may want to give further attention to.
T206 Resource has all the back variant info, along with other stuff
http://t206resource.com/Article-T206...ltipliers.html