Very WW2 U.S. Handwritten Postage Letter

this was a rae thing to have the postage Handwritten even after WW2. This letter is to my grandfather , a Col. Army Air Corp (before air force) thanking him for his service during the war.As he had an established Attorney Practice in Texas. Everyone in my immediate family is gone and I'm offering it for sale to a serious collector, one with a very large collection .