25c Transpacific China Clipper bottom plate block of six
Four plates were used to print this air mail stamp issue. They are 21473, 21474, 21475 and (shown) 21476.
This bottom margin of a plate block contains six stamps illustrating the Martin M-130. Only three such airplanes as were actually built. They were named the China Clipper, the Hawaiian Clipper and the Philippine Clipper.