The VR56 is a pre-WWII UK RAF receiving pentode valve. The VR prefix in the type designation stands for Valve Receiving.
The valve in civilian name is an EF36 and this exhibit looks like a Mullard device from the size and shape of the envelope. This valve was obsolete by the 1960s.
The gettering obscures the electrodes, but here the pinch and shield can be seen.
The classic envelope is 30 mm in diameter and, excluding the IO base pins, is 86 mm tall.
References: Datasheet & 1040.