A dumbbell shaped valve with a narrow middle section.  The "NE" prefix suggests that is is filled with neon gas.

The top brass node appears to be connected to a circular internal node whilst the bottom copper node has no internal connections at all and is insulated by the glass bulb.

The device would probably have been used in some more elaborate "measuring stick" device, so I think this was a plug-in component.

The design would be consistent with a neon gas discharge tube which you would expect to glow at high voltage, the narrowed neck accentuating the plasma glow and hence making the indication of high voltage easier to see.  Therefore you would earth the brass (cathode?) end and use the copper end to sense high voltages (which is probably rounded to stop corona (thanks Mike)).

Accompanying the valves is an Ediswan Industrial Valve Service Report Form (Form 1309 Revised).

This 365mm x 203mm thin sheet had to be filled in with quite a bit of detail to return a faulty valve.  Such things as model and serial number of the equipment it was in, numbers of hours of use, filament voltage when in standby mode etc.

The return address was The Edison Swan Electric Company Ltd., Radio Stores, Ponders End, Middlesex, England.