At some point in time, this bulb was a non-working, tipped Westinghouse Mazda bulb with a tungsten cage filament. It was picked up by a bulb recycling company in the 1910's (possibly SYLVANIA, a company that started out recycling bulbs), which then made a big hole on top, snapped off the glass rod and pulled out all of the contents, fitted in a new carbon filament and then finished the job by evacuating the air from the hole on top. Such companies could only fit in new carbon filaments because they require no supports (contrary to the brittle, long uncoiled tungsten filaments which need many supports). It can be a confusing item, since many recycled bulbs are etched with "Mazda" (like this one), and all Mazda bulbs had tungsten filaments. It seems that these recycled bulbs were quite popular, as they are not that hard to find on eBay. This 3 loop filament variant is a little harder to find. The tip of this bulb is larger than normal, because the hole made on top needed to be large enough to fit in the tools to attach the new filament in place using carbon paste.