Webb A21(old# A22), 10c Blue Plane over Globe Air Letter Sheet (Aerogramme), unused, Cat. $25, watermarked
“first fold here” line centered at left of vertical fold guide line
small number 39 at LR of back flap, likely a PO counting number (workers would often number their stock sequentially so as to keep track of quantities on hand and not have to count them all the time)
