The only thing I could find digging around quick is referencing the 55th MP Co. Apparently, they processed a lot of POWs.
ETA: If he was with 55th, there should be a second set of ribbons, likely just one or two, with gold braid around the edges. They're unit commendations.
http://www.history.army.mil/html/forcestruc/lineages/branches/mp/0055mpco.htm
ETA Again: The Nike system went into service in '54, your dad was obviously in well before that as he'd have served before '46 to get the WWII Victory Medal. Do you know what he did before working on the Nike?