The VS68 is a four in one voltage stabiliser that GEC marketed as the Stabilovolt. The commercial designation is STV280/40 and has a maximum current draw of 40 mA. Also made was the STV280/80 with higher current rating.
It has four anodes, and thus four outputs with gaps of 70 volts each. These output voltages are 70, 140, 210 & 280.
The striking voltage is above 420 Volts and the tube current is 5 - 35 mA. The tube voltage regulation is about a couple of Volts for each 70 Volt step.
The pinch showing how the leads to the cathode and four anodes are shrouded in glass as far as possible.
The inner cylinder has a domed top. The VS stands for Valve Stabiliser and this valve made for the RAF carried the Crown and A M.
The wide glass tube envelope is 47 mm in diameter and, excluding the B5 base pins, is 123 mm tall.
References: Data-sheet & R J Sutherland.