The UY85 half wave rectifier was designed for use across the European mains, as the 100 mA heater suggests. The reservoir capacitor specified is 100 µF and the minimum effective series resistance in the circuit needed to be only 100 Ohms.
The design use was in domestic broadcast receivers for the main HT rail.
This example is of a UK made valve.
The anode is folded out at the ends revealing the bright inner surface.
The anode full face showing how the two halves are stitched together.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 59 mm tall.
References: Data-sheet & 1040. Type UY85 was first introduced in 1954.