Original "Airplane Radio Telegraph Transmitting Set" Type SCR-73 - Signal Corps Radio Pamphlet No. 13. Covers rotary spark gap set SCR-73 installed on a plane. 16 pages, dated June 30, 1918. Good to very good condition with callsign 8EU stamped on front cover - see photos. Pamphlet size is 4.5" x 7.0".