Bidspirit auction | Worldwide Air Post Stamps and

Worldwide Air Post Stamps and Postal History - United States - 1989, 20th UPU Congress, Futuristic Mail Delivery, (45c) multicolored, bottom right corner sheet margin se-tenant block of six, containing block of four and horizontal se- tenant pair with light blue (engraved) color omitted, full OG, NH, VF, C.v. $475 for block of 4, Scott #C125b, C122-23 var