Elmwood 2450 Thermal Sensor, these are NORMALLY OPEN. The part number is 2450 87-265 F131. They close at roughly 55°C. Used in the Hafler DH500, P500, and XL600 audio amplifiers as a thermal switch to increase the speed of a cooling fan when the amplifier temperature got hot enough; so it's NORMALLY OPEN (we verified that it is) and then closes when it gets hot enough (roughly 55°C), in the Hafler case, increasing the fan speed by bypassing a resistor. Hopefully that gives a general idea of it's temperature operation. In case it helps, this sensor goes by the Hafler part numbers SWH-119 or SF025; both are the same sensor.