This is a Packard carbon light bulb (There's a Packard label on the inside of the base) with a Thomson-Houston base, one of the base styles that became popular in the 1890's. Bulbs with this base type are only a somewhat common find. This particular bulb has an intact filament, yet no continuity. It is held together to its base with plaster, and is insulated at the bottom with porcelain.

There are many different variations of the Thomson-Houston base. There's even one that is made entirely of porcelain. Most T-H bulbs were made before the year 1900. At that point in time, their remaining market share was about 10%, and by 1905 they were gone completely, due to an aggressive campaign to replace this base type with the Edison base, through the use of TH-to-Edison base socket adapters (see my Thomson-Houston socket pages for more information).

T-H bulbs with the full porcelain base variety seem to be more recent than the brass type, but I am not sure. Some of these use cement (instead of plaster) to hold the bulb to the base, which indicates post-1900 manufacture.

Thomson-Houston bases might look much larger in pictures than they really are to some people. Someone who has never seen one in person might think they are as large as a mogul base, but they're not. Actually, they are only slightly larger than a regular Edison base. Finally, T-H base bulbs are unique for the fact that they can be displayed very easily, as they stand upright by themselves.