This exhibit arrived in a box stating that it was a mystery Philips valve. However, the overall impression is that it looks like the Frelat valve seen here.
The format follows the R Type with horizontal cylindrical anode, helical grid and single strand filament. The base shell looks to be copper and fixed to the inner composition insulator by screws.
On test the filament takes 0.2 A at 1.8 V and this indicates a thoriated tungsten filament and so an early dull emitter.
As the shape matches early continental R Types but the filament is thoriated tungsten, it is possible that this is a development valve. The metal base skirt screwed to the inner insulator is also different to standard production valves of the time.
All electrodes are held in the pinch with the supports strengthened by twisting the wires together.
The grid helix is self supporting with the wire ends being held by folds at the ends of the supports.
The anode is an open cylinder with the twisted support wires opened out and passed through two holes in the anode flange and folded over to form a seal.
The copper base shell and simple brass split pins for the base connections.
The wires are soldered to the brass pins.
The balloon envelope is 51 mm in diameter and, excluding the B4 base pins, is 78 mm tall.
