It is a common type of carbon filament bulb, made by Fostoria and probably 16 candlepower. It isn't scarce as bulbs go and has little value, but looks to be in good condition. From the closeup of the press (i.e., the pinched part of the stem through which the wires pass from the base into the bulb), you can tell that there is a small length of platinum wire going from partway inside the press to the carbon paste blob that attaches the filament. Platinum was used because it has the same coefficient of expansion with temperature as does the glass. Because platinum was (and is) expensive, manufacturers eagerly sought a cheaper alloy or composition. One called dumet was invented, was first used in 1913, and is still used today (James, correct me here if something else has taken its place). So it is safe to say that your bulb was made before 1913, but probably after about 1906 (before then the platinum wire tended to be longer and to pass all the way through the press).
