The 2018 UPSS catalogue reports three mint entires in this size, one with round gum on the top flap and two with square gum. A total of only three combined are reported in the larger sizes (sizes 10, 21 and 25, latter two with stains or toned). This is another key item to a complete postal stationery or Officials collection.
Ex "Scarsdale". With 2000 and 2013 P.F. certificates. UPSS value $45,000.00