Hmmmm. I went right to the source on the Air Force Personnel Center website. Here is exactly what it says..."This medal (pictured below) was authorized by Congress on July 6, 1960, with the creation of the other medals of the Air Force. The medal was not created until June 1, 1963 when the Secretary of the Air Force established it." I guess the Air Force Personnel Center should have contacted you first before publishing facts of history. Of course, as I suggested in my previous post to you, it is possible that the medal was awarded retroactively which could explain why you have it listed on your DD214. Just to clarify for you...that isn't a bad thing and it doesn't mean you weren't entitled to or actually awarded the medal. So put your hackles down and relax.
I don't know why I bother, but the Air Force and the Army shared the same GCM medal for some time.
The last of the Good Conduct Medals is the Air Force Good Conduct Medal which was authorized by Congress on July 6, 1960, but not created until June 1, 1963. Between 1947 and 1963, Air Force personnel were issued the Army Good Conduct Medal. For those serving both before and after 1963, both the Army and Air Force Good Conduct Medals could be worn simultaneously on an Air Force uniform. In 2005 the medal was discontinued by the 97th Air Force Uniform Board, and is no longer issued. However, medals that are a matter of record may still be worn
Some branches of service interchanged medals. For example, the Navy Cross can be awarded to Army personnel. Prior to 1960, the USAF may have used the Army's Good Conduct Medal to award to their own personnel before the AF had their own medal to award.
Such things are not impossible.