The UU10 from Mazda is an indirectly heated full wave rectifier on a B4 base and the design dates from 1951.
The anodes are shaped for rigidity of the thin nickel sheet.
The twin rectifier section placed side by side.
The round cathode tubes are joined by a bar above the top mica. The heater is a single insulated hairpin.
Here the oxide coating on the cathode tube can be seen within each anode. The central cathode joining bar connects to a vertical rod that is the cathode connection.
The classic envelope is 45 mm in diameter and, excluding the B4 base pins, is 104 mm tall.