Good Conduct Medal

This information was provided by Neil Ablesma with the Marine Corps Air-Ground Museum in response to a request by Peter (Jack's):
"This is a mixture of various decoration and service medals. The medallion is the Marine Corps Good Conduct Medal. The bronze suspension bar (US Marine Corps) that you [show] beneath the Eagle, Globe and Anchor hat device ... is part of the decoration. ... The suspension ribbon is for the World War II Victory Medal. The bronze star on the bar and the missing one are in lieu of the clasps authorized."

So, it sounds like this is an agglomeration of parts and pieces, but the medallion (despite the wrong suspension ribbon and bar) is the Good Conduct medal.