This is an original Edison GEM bulb. In the very beginning of their existence (in 1905), GEM lightbulbs had twin hairpin filaments in series (like on this bulb). They were later changed to a single continuous filament, in 1909. This means that this bulb is at least 101 years old, and could be up to 105 years old! The GEM bulb used a filament that was 25-30% more efficient than the carbon filaments used in earlier bulbs (they gave more light and used less power) but were later left in the dust by the much superior tungsten filament, which appeared in 1907 and is still used today. See my other Edison GEM bulb
. The higher wattage GEM bulbs (like this one) disappeared first, the smaller sizes were produced until 1917. This is why this bulb is so rare. The GEM filament is the work of Dr. Willis R. Whitney.
Westinghouse also made its own version of the GEM bulb, which was called the "Westinghouse Metallized" lightbulb. It is interesting to note that GEM filaments are extremely springy, much more than normal carbon filaments, and appear to be quite resistant to rough handling.