71 is actually a later short name - somehow incorrect - but probably found on schematics. Tyne page 315: "The design of the UX171 was started early in 1925. It followed the construction of the UX201A rather closely and had a thoriated tungsten filament operating at 5 volts and 0.5 ampere. At the maximum recommended anode voltage of 180 volts, it would deliver 0.7 watt output. In October 1925 it was adopted by RCA but was not advertised or sold to the public untl June 1926. In November 1926 it was replaced by the UX171A, which had an oxide-coated filament operating with 0.25 ampere at 5 volts." But follows: "At the time the UX171 was brought out (May 1926), RCA also announced a new detector tube, the UX200A, to replace the UX200.
