The UR1C is a half wave rectifier designed for 200 mA series connected heaters as found in AC/DC radio receivers - needed before AC mains was universal after the completion of the National Grid.
The anode voltage is the RMS value and the maximum heater to cathode voltage is 350 Volts.
The reservoir capacitor can be 16 µF with an effective minimum series resistance of 75 Ohms. For a 32µF capacitor the series resistance must be a minimum of 125 Ohms. The heating time is quoted as 70 seconds, this gives time for all of the valves to heat-up before HT is applied.
The literature gives the UR1C as an equivalent to the 1D5, and most respects it is, but the ID5 has a 40 Volt heater at 200 mA.
The carbonised anode does not fill the width of the envelope.
Seen frm the side, the active cylindrical region is quite small - about 3 mm in diameter.
The classic envelope is 40 mm in diameter and, excluding the B5 base pins, is 100 mm tall.
References: Data-sheet, 1040 & 1043. Type UR1C was first introduced in 1935.