This image shows a cowboy aboard what appears to be an Appaloosa roan horse while he watches over a modest herd.
The description states:
No. 4005 – Cowboy watching herd of cattle on a mountain meadow.
–The image was published by a Colorado company, and was sold to tourists in Little America, Wyoming. The black staining in the upper left is from the cancellation machine, as this card was used. The postmark is dated June 17, 1955.