This is a US GI (Government Issue) Military Thermoelectric Tent Fan (also called a TEF or stove-top heater fan). Great for tent stoves! What it is: It’s a self-powered circulation fan designed for US military tent heaters (like the M1941 or similar flat-top modular heaters). It sits directly on top of a hot stove/heater surface. No batteries, electricity, or fuel needed — it generates its own power using the thermoelectric effect (heat difference across a module creates electricity to spin the fan).