This exhibit carries the Marconi name but was in Canada by RVC.
The U52 is directly heated full wave rectifier with a rating of 500 Volts on the anodes and a PIV of 1,400 V. The U52 has a maximum reservoir capacitor rating of 16 µF and a minimum series resistance of 180 Ohms.
The Marconi paper label with Made in Canada etched in the glass. Looking at the label from the back the glass actually carries the Type designation of VU71. The VU71 being a pre CV UK service code. This then dates this valve to before 1941.
Side view of an anode.
The filament is an oxide coated ribbon mounted as an inverted V.
The top mica showing the top of one filament and the supporting tensioning spring holding it.
The classic envelope is 52 mm in diameter, and excluding the IO base pins, is 119 mm tall.
References: Datasheet, 1040 & 1043. Type U52 was first introduced in 1938.