This is a really cool postcard and I would love to own it. With that said, I was watching the old game show "password" the other day and this thread made me think about that show and the fact that they could use this Auction as a clue for the word "Hype"
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But kidding aside, I am in the camp that this was produced sometime after 1907. Unless an example is found postmarked earlier, it is hard for me to imagine they produced these when the picture was taken with the intent of selling very many. When he made it big, someone probably had the bright idea to produce these cards of the legend that passed through Idaho (IMO).
And to JimB's point, did someone need to state that they were producing a commemorative issue back in those days?