WW2 or possbly a little later.  Stamped with the 82nd Airborne Public Information Office return address stamp for Fort Bragg as shown.  Might be later because of the addition of the "PMGC" underneath the penalty statement on the right.  Most I see from WW2 do not have them but I do not know when they started putting this on them.  I think PMGC stands for Post Master General Chief.

Each measures approximately 9” x 4”