Webb A1 (old# a4), 10c Blue George VI vertical 3-panel Air Letter Sheet (Aerogram), unused, Cat. $125
neatly folded, tiny stain on upper flap at left visible only when unfolded
differentiated from A2 as this has the square corners on the bottom flap (see scan)
differentiated from A3 & A4 as the top and side sealing flaps have rounded ends and not the straight line angle cuts
