The 2B from AEI is clearly a barretter or current stabiliser and was made in the UK. Inside one can see the fine wire is coiled and held by a central support. This inverted V arrangement exists in two separate electrodes and four base pins are provided.
It is possible that this twin arrangement and the special base point to an industrial application and not just to stablising the heater current in a series heater chain.
The special base and connecting pins. Clearly this pushes sideways into the holder.
The pair of coiled iron wires. The gas filling will be hydrogen as is typical for all barretters.
A clearer view of the wire coil.
The wide glass tube envelope is 25 mm in diameter, and including the base pins is 81 mm tall.
Updated December04, 2014.