This is a brand new Rheem/Ruud/Weather King/Corsaire Furnace Upgraded Furnace Limit Switch. It is rated at 105 degrees (L150-10F).
A limit switch is a safety device designed to shut down a piece of equipment. Limits have a set point, which is in some cases, adjustable. The set point prevents the temperature or pressure from exceeding the rating of the switch.
47-22860-01