The UV-213 was an important tube in the history of radio as it was the first of the commercial full wave rectifiers. The UV-213 evolved into the UX-213, which in turn was redesigned into the UX-280. The type '80 spawned numerous other rectifiers, which differed in basing and detail specs but had essentially the same basic design. These rectifiers were in use until the end of large-scale tube manufacture.
Design work on the UV-213 full wave rectifier was started by GE in the fall of 1923. The initial specs were very modest, only 10Ma output at 90-100 Vdc. In December of 1923 RCA approved the designation of UV-213 for this tube. As shown in Fig. 1, the early design had a brass base and tip, and an unusual (for GE) bulb style. Long, small diameter plates were used, with a series connected filament for the two plates. The filament was thoriated tungsten, and drew 2 amps at 5 volts. There was no marking on the exterior of the tube, but UV-213 was marked on the press.
A somewhat later version is shown in Fig 2. The base had been changed to a bakelite UV type and no tip was present. The plates were positioned further apart and an improved filament support structure was used. The same unusual bulb is used. As with the earlier version no marking is present except on the press, which is once again marked UV-213.
During the development of this tube the output voltage and current requirements increased substantially and by the time the final design was decided on (summer of 1924) the specs had changed to 65Ma output with a max input of 220 Vac per plate. It is presumed that this final design had the internal structure of the UX-213, see Fig 3. This version had shorter box plates and a much more robust mechanical design than the earlier versions. RCA was not particularly interested in this tube, and it languished for more than a year, being finally released for sale in September of 1925. By this time the UX base had been adopted and the released version was coded UX-213.
The UV-213 then was never sold to the public and surviving samples are in the nature of engineering prototypes. These tubes are relatively rare and probably often unidentified due to the lack of external marking. Fig. 4 shows a close up of the press area for both tubes. It required considerable experimentation with the lighting plus tweaking in Photoshop to bring out the UV-213 marking. The brass sample was purchased by the author many years ago as an "unknown brass base rectifier" and only after careful examination was its true identity discovered.
Reference: The Developments of the General Electric Company of Radio Receiving Tubes, March 1, 1929.