Panama Canal Zone C15-C20 blocks/4

USA Panama Canal Zone C15-C20 blocks of 4, MNH, $370.00. Michel 97-102. Air Post 1939. 10th Ann. of airmail service, 25th Ann of the opening of the Canal. Douglas plane over Sosa Hill; Map of Central America; Pan American Clipper, Fort Amador; Cristobal Harbor; Gaillard Cut.