I went back for the 50's (unless I'm royally effing up my tag reading) camo. I don't have any idea what the practical use was for this but it appears to have snaps on the bottom for snapping into/onto something else. It also has some interesting loop thing on the back which I have a picture of. In one of the pictures you can see the messed up snap. Still very interesting. I've got a closeup of the only tag I can find on it. It was worth grabbing for $3 just to examine closer if nothing else. If anyone has any ideas as to what this is let me know!
EDIT: When I search A.B.L. I'm getting hits for Belgian army clothes with what appear to be similar camo patterns.
EDIT 2: It appears that this is what's called a paratrooper smock.
You have a PM.