Vintage WWI Airplane Radio Receiver Type S.C.R. 59 BC-12 - US Army Signal CorpsThis unit was manufactured by Western Electric in 1917-18 for the Signal Corps of the US Army under the order number W40761. This kind of radio receiver was installed in an airplane to allow a pilot to receive instructions transmitted from the ground by an SCR-67 or compatible transmitter . It measures 13\" x 9 5/8\" x 5 1/2\". The top panel is free of damage. The box has the original finish. The unit has all original brass plaques and hardware. The tuning dial and the band switch turn freely. The two pull switches operate smoothly. With the exception of three missing parts, all components inside appear original. The missing parts are: the plate choke coil for the first audio tube, the condenser and grid-leak assembly for coupling the first and second audio stages and a spare condenser grid-leak assembly. The grid-leak value is about 2 megohms and the coupling condenser is about 0.01 microfarad. Details for constructing a replacement choke can found in an article by Arno Kluge in Wireless Age, June, 1920. The choke consists of 25,000 turns of No. 38 enameled wire, wound on a 2-inch long iron core with 1/2 inch diameter, and is enclosed in a soft iron case.Included in the radio are three tipped tubes with good filament: a DeForest Audion tube with isolanite base and long pins and two OT1A tubes with tubular plate, brass base and short pins. One OT1A has no vacuum. O&T Electric Corp. claimed that the OT1A tubes were manufactured by DeForest. These bootleg tubes were advertised for a few months in 1924 until O&T got sued by DeForest.This unit is being offered as-is. Except cleaning and the identification of missing components, no effort was made to bring the set to a working condition in order to characterize its performance.