VX371 voltage stabiliser

This valve measures 76x31mm overall and has a B8G base

There are no electrical details for this developmental valve. The label reads "This valve is supplied by the Development Laboratory of MARCONI'S WIRELESS TELEGRAPH COY. For Laboratory and experimental purposes without any obligations as to further supplies or manufacture." The valve is marked with the serial number 648. Compare with VX370, which appears to be the same device with a different internal structure.