The STV280/80 is the larger of the two Stabilovolt voltage stabilisers made. The smaller STV280/40 was most commonly found with the service code VS68 and had a maximum current of 40 mA whereas this stabiliser is rated up to 80 mA.
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 opalescent glass has a soft feel to it. There are no markings - and I looked for the R Lalique signature!
Diagram of internal construction.
The wide glass tube envelope is 61 mm in diameter and, excluding the B5 base pins, is 135 mm tall.
References: Data-sheet & R J Sutherland. Type STV280/80 was first introduced in 1936.