That is a "snap disc" bi metallic switch that turns on or off depending on temperature. I'm not sure what it is for either. Is the AC factory install or dealer AC?

The form factor of the switch is super common and still used today. In fact, the 2455R series comes up as a Honeywell part, see links below then look for your part #, it should be there somewhere.

2455R-100-89 HONEYWELL S&C Temperature Switches | 98K8376 | Newark element14

www.farnell.com/datasheets/93692.pdf

sensing.honeywell.com/product-page?pr_id=53358