I have always been under the impression that this is a postcard. My version has the “photo post card” back as do the other PSA graded examples I’ve seen. However I just watched this copy end on eBay well above what I would have expected a sale to be, and the back is blank:
https://www.ebay.com/itm/1950-56-J-J...-127632-2357-0
Is this a variation in not aware of? Or is one type not authentic?