Carbon wire filament incandescent light bulb

This carbon wire light bulb was created after the merger of Edison's and Swan's companies to form Edison & Swan United Electric Light Company in 1883.
The two indentations in the glass of the bulb are intended to make the plaster adhere better to the connection between the shell and the fitting. On this bulb the fitting is missing.
Carbon filament lamps were the first incandescent light bulbs, in which a filament emits light when heated by an electric current. Thomas Edison and Joseph Swan were both pioneers in the development of the light bulb. The filament must be kept in a vacuum to prevent it from burning up, and this is why the filament is enclosed in a glass bulb.