This is a Brand New Trane / American Standard 3" Main Limit Switch rated at 155 Degrees (L155-30F) . The Part number is C340056P18 and/or SWT01280. Thanks for looking and good luck!
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.
155 L155-30F SWT1280 SWT01280