Hammer lamp No 1903-778 shows a 1903 version of a titanium carbide lamp invented by William Lawrence Voelker, an American citizen. An article in the Electrical World and Engineer, Vol XXXIX, No 1, Jan 4, 1901, pg 42, gives a few details about this lamp.

This new lamp was introduced to the public in England (note the double contact Ediswan base). The length of the filament was shorter than a corresponding carbon filament. The claim was that the filament was both tough and elastic. At the time of the article the conclusion had been reached that the development had proceeded to the stage of manufacture. It was claimed that the lamp showed very little darkening during life.

A filament of the carbide had been developed for 500 volts. This was a marked departure from the carbon filament lamp. At such a high voltage arcing would usually proceed between the leads coming out of the stem press. To help reduce or eliminate the possibility of arcing the bulb was made bifurcated as the EW&E drawing, shown here, indicates.

It was also found that lamps made for such a high voltage required the socket to be better insulated.