The top one is a spare I carried in my boat that was raw water cooled , and the bottom one came out of my closed cooled engine in my new boat. Are they interchangeable?
Both are 160 degree.

Closed Cooling Diagram

They are different. The brass looking one has a disc on bottom that closes/opens a passageway. The stainless looking one does not.

Thanks SB. I have seen that disc before and always wondered what it was for. I assumed it was to help the thermostatic spring, like new and improved or something.
I just shined a light in the housing and, yep, there's a passage to open and close.