It is incomplete. Found 1 other of this same part in the Ebay completed listings. However no real info there either!
http://www.ebay.com/itm/231769802790
Yours has the button on the side but the back is different. Yours also seems to be missing the change tray.
Unless anyone else here knows, you probably will need to find a coin-op forum or another collector or company that works with items like that.
EDIT: I made a thread for this on KLOV, we'll see if anyone there knows anything.
http://forums.arcade-museum.com/show....php?p=3237266