May we see the whole cover?
As far as the cancel, it's a Prescott, Arizona "horse and cowboy" fancy cancel, that I believe was philatelically contrived, as the internet shows others with similar cancels and with the same backstamped date of October 24, 1928:


The return address on the back of your cover is to (Dr.) A.W. Bork, who was a noted historian in Prescott, Arizona and has co-authored several articles and books about the famed Wyatt Earp and Doc Holliday and their women, most particularly Mary Cummings a/k/a "Big Nosed Kate Fisher", who he interviewed in 1935, while a graduate student at the University of Arizona at Tucson:
http://en.wikipedia.org/wiki/Big_Nose_Kate