Worldwide Air Post Stamps and Postal History - United States

Worldwide Air Post Stamps and Postal History - United States

1998, Space Shuttles, imperforate proofs of $3.20 in magenta and $11.75 in cyan, two sets of two values in left sheet margin vertical pairs, printed on coated and uncoated paper, no gum as issued, NH, VF and scarce, C.v. $900 for stamps on uncoated paper, pairs on coated paper are priced with ''-'', Est. $1,000-$1,500, Scott #3261-62 Pa, Pb