four preliminary stamp-sized pencil drawings of unadopted designs, 50c without vignette and three 25c designs showing the Gaillard Cut with an airplane overhead (as with the finalized design), each of four designs 25x30mm, signed "Trace D, 18 Nov. 29, Bolton", very fine, one of three reported preliminary pencil drawings of this issue

Meade Bolton, architect with the Panama Canal Company, prepared the common design for the first permanent airmail series stamps as requested in an October 7, 1929 memorandum.