Coop, there is no such thing as a “former Marine”; once a Marine, always a Marine. So I believe that the correct appellation for Tyler Kistner is *retired Marine*.
Negative, Ghostrider. You're chatting with a former Marine. The phrase is "There's no such thing as an ex Marine." (Even that's not true. Lee Harvey Oswald and Jack Murtha are examples of ex Marines.)
"Retired" covers people who do at least 20 years or are medically retired (with pension). There are a lot of us who are simply Marine veterans (less than 20 years of USMC service).