New White-Rodgers 3L01-120 snap disc limit control.
https://ebay.io/m/8sg5r5
Replacement Aquastat Switch. This Emerson Climate Technologies thermostat has a fixed setting with an open temperature of 120 degrees F and a close temperature of 110 degrees F. The unit is a 3/4 inch disc type with a silver-colored metal mounting flange and two electrical terminals.