Original linen-backed patent lithograph for the Pioneer Instrument Company's improvements in engine synchronism indicators, one page, 12.5 x 10.25, August 11, 1932. The diagram features multiple views of the improved indicator design, as well as its connection to the aircraft. The top border reads: "378,242 Complete Specification." The lower border features the printed text: "Charles & Read Ltd. Photo-Litho." The left border reads: "This Drawing is a reproduction of the Original on a reduced scale." Includes the printed British "Patent Specification" document, seven pages on four sheets, which describes the invention as a method for reducing interference caused by radio transmissions, in addition to several other objectives. The specification sheet bears a "U.S. Patent Office Library" ink stamp on the first page. In fine condition.
