Stokes page 17: The first tubes with thoriated filament made by General Electric (GE) appeared as UV-199 and UV-201A. They were produced late in 1922 but were not available for general sale until well into 1923. The Radio models Radiola II and IV were delayed until the Christmas selling season 1922 due to shortage of UV199's.
The UV199 uses a unique small base which never was used for other tube types. The UV199 is the first tube intended for use in portable receivers as well as in home receivers using dry batteries. The filament is for 3 volts, 0.06 amperes. After a year of release this was rated to 3.3 volts. Physically the UV199 (also called 199) is much smaller than any previous GE tubes (T-8 tubular bulb). Initially a brass base was used. Tipless bulbs were introduced early in 1924 and bakelit bases came into use during October 1924.
In August 1925 the UV199 was fitted as UX-199 into the standard UX style base, fitting the UX socket but having much smaller diameter and in addition has a characteristic reverse taper shape. Therefore the UV199 had still to be produced for replacement. In 1932 UV199 and UX199 got a shoulder glass bulb and are then called V99 and X99.
