Your lamp is an early form of reflector lamp, made by Osram-GEC in London around 1925. It was marketed as the Osram Axial Type lamp, and the filament is arranged into a better defined ring than with standard types. Similarly the glass bulb is shaped such that an external reflector, usually made of white Russian opal glass, could be brought relatively close to the filament. This served to project a concentrated beam of light out the front of the lamp.
The tungsten filament itelf is of a very early type, evidenced by the heavy degree of sagging between its support wires. By the 1930s tugsten metallurgy had improved tremendously and such severe sagging was no longer commonplace, thus dating your lamp to before this period.
You will probably find two numbers printed somewhere on the glass, usually inside a circle. With this information I could precisely give you the year and month of production of your lamp. Do you also have a collection or would you consider selling on this lamp?
Best regards!
James.
