Although in non-working condition, this bulb appears to be a rare and collectible Westinghouse-Based, 19th century Sawyer-Man lightbulb. Westinghouse-based bulbs in working condition are quite sought after. Since this particular example is not in working order, it is not worth nearly as much, but it is still a real 120+ year old bulb.
This bulb has a unique, Y-shaped stem and is insulated at the base with porcelain. I believe this stem design is a Sawyer-Man design. Bulbs insulated with plaster instead of porcelain also exist, but those are even more costly to obtain, even if they don't work. Sockets for this type of bulb are also expensive. This bulb contains a squirted cellulose, hairpin-shaped, carbonized filament, which looks very much like a black cotton thread when viewed up-close.
Westinghouse bases may appear to be much larger in pictures than they really are. A person who has never seen one may think that they are as large as a mogul base, but they're not. Actually, they are the same size as a regular edison base (the common base type we still use today).
So, this is everything I know about this bulb, and as you can see, it's not much. If you know more about this bulb, please don't hesitate sending that information in.