Ol' Rube must have been having a tough day...got a little confused and signed it twice! Or maybe he wanted this one to be twice as valuable...
In all seriousness, it looks like someone tried to forge his signature, failed, and then tried again. I bought this one on ebay with no expectation of it being an authentic signature; I just needed it for my collection and the price was right (i.e., cheap).
It is an authentic T206 at least. Back is Sov 150 with some paper loss. For me, the "signature(s)" just add character.
mm