Check the actuator housing for the model number

it manages a broad 2

including speed nuts and Allen screws required for a professional install

This part number typically refers to the thermostat chassis and wall plate

Lochinvar & A.O. Smith 100233591 Immersion Thermostat 326058-755 Check the actuator housing forThe Lochinvar & A. O. Smith 100233591 Immersion Thermostat is a precision engineered OEM replacement temperature control designed for high performance water heaters and commercial boilers. Operating within a critical 80 180F temperature range (or up to 210F depending on specific kit configurations), this immersion style sensing probe utilizes a 1 2 inch NPT stainless steel connection to ensure accurate thermal transmission and rapid response to fluid