Alien artefact?

My grandfather had some links with the military in the US in the 1950's (I know next to nothing about him. I don't think he worked for the military but he was some kind of consultant) anyway whilst clearing a box of his things we discovered an old photograph amongst some postcards that is certainly intriguing!

If nothing else it's an early example of a hoax perpetrated by the military as some kind of cold war subterfuge? That's my theory anyway!

There is some writing on the back of the photo that reads "Sub 3, 14th June 47 MJ J (then faded but looks like) Marcel (then at base of photo a stamp of some sort & numbers 595542 57 632 12

(the original photo had a border but I had to crop this to be able to upload)