This exhibit carries almost no identification. In very faint etching can be seen SS 4.3 V 0.06A only. The SS may not be the correct Type designation but it is all we have at present.
The filament is intact and glows bright orange at 4.0 Volts and 0.07 A. This would make the single strand filament thoriated tungsten.
Aurora was a brand name of Gloeilampfabriek M Heussen & Co of Arnhem in the Netherlands. They started making valves in 1921. This valve was clearly made for export as the wording on the box is in English. Frelat was another brand of the same maker. The 1928 advert for Frelat has a general purpose valve taking 4 V at 0.07 A and this exhibit may be the same valve.
The magnesium gettering makes looking at the horizontal electrodes difficult. The grid is a series of flat strips held on circular end pieces. Within the anode the strips form a shallow barrel shape.
The grid end piece.
The left of this image reveals the very thin filament. One of the grid strips is also just visible
The wide glass tube envelope is 41 mm in diameter, and excluding the B4 base pins is 84 mm tall.
