UNITED STATES Graf Zeppelin set. C13-C15 – set of 3. Used – clean backs. Sound stamps – no thins or tears. The free listing tool. The item “US C13-C15 used GRAF ZEPPELIN set of 3″ is in sale since Thursday, March 08, 2018. This item is in the category “Stamps\United States\Back of Book\Air Mail”. The seller is “gemadastamps” and is located in Salem, Oregon. This item can be shipped worldwide.