Hi Cole,
In terms of front/back combos I found this
link on T206.org to be extremely useful. I'm not sure when it was last updated but it has helped me verify front/backs on many of my T206s. I'm with Iggy that you really need to see and feel the card to know for sure if it's authentic. In many cases, scans don't do justice to the cards in terms of colors, creasing etc.
That said, I'd be surprised if the Cobb in question is not authentic although David's expertise on these things and observation on the white border has me scratching my head.
I went back through some of my "torn" T206 cards and none exhibit that very white border. In fact, they do tend to be darker as mentioned in David's post. I've flip flopped a few times but perhaps it is a reprint.
Regardless, I think there are a lot of good resources that have been mentioned on this thread. Take care.
George