US #921 Overrun Nations "KORPA" Error

1944 Mint Block of 6
When the Korean Overrun Nations stamp was released in 1944 a printing plate flaw made the E in KOREA appear as a P, hence the KORPA error! Only one out of every 200 stamps contains this hard-to-find mistake. Kenmore has located a limited supply of this scarce issue as a single error in a block of 6! (#921)