Categories1 of 3 Kown Sets! C27-31 with Mauritania UPU Specimen Overprint. A great Rarity with the set that was issued for and used for flights in and out of Hawaii. RARE! 21_88_Specimen(C) 4/17/20 21-88 1 of 3 sets C27-31 Specimen$500.00PriceQuantityAdd to Cart