This bizarre object is made by Tempco, a Chicago-based manufacturer of heating elements. It's called an Edison-style Ceramic E-Mitter, and as you can see, it has a lightbulb form factor but provides no illumination.

Instead, you plug its E26 butt into a porcelain or ceramic socket, and it starts kicking out infrared heat. It's essentially a less fragile, non-light-emitting version of the red heat bulbs people use to warm their lizards. By not giving off light, this doesn't disturb the animal's circadian rhythms.

That's not its only application, of course. Bulbs like these are used in industrial, shop or production environments where workers need to safely spot-heat a material; think warming a silicone mold before casting resin, softening plastic tabs before bending them, pre-heating a sheet before thermoforming, loosening up solvent, etc. The user can rig up their own fixture, provided they use a porcelain or ceramic fixture. (The base gets too hot for a plastic fixture.)

The bulbs aren't cheap at $28 a pop, but they last for around 10,000 hours; in contrast, red heat lamp bulbs often give up the ghost after a couple thousand or so.