A card with multiple personalities.  You can see the front, with a Cheyenne, Wyoming postmark.  But the card was mailed from Chicago to Cheyenne in 1906 (with stamp and postmark), there are a total of three postmarks on the back (two days from Chicago to Cheyenne, not bad), and a rubber-stamp indication “Denver, Colo. Forwarded”.  It’s interesting that there is no forwarding address, so did everyone know where everyone else was in those days?  Hard to grade.  Call it:  Grade: 3