The UABC80 is a triple diode triode in a miniature envelope.
It can be seen in the photograph that three separate valves exist within the envelope. The triode is on the right, the single diode at the other end. In the middle is the double diode, with each half of the box anode insulated from the other.
All three sections have the same width and thickness. The struts at the left connect to the heaters.
The UABC80 and its 300 mA brother PABC80 were specifically designed for use in the detector stage of early FM and FM/AM radios. Normally this valve featured in a ratio detector circuit for FM demodulation and a diode detector for AM as well as the first stage of audio amplification.