I pulled this out during my coolant reroute. Seems like a better design than most. Large opening (32mm) for more coolant flow. Haven't had any luck with Google, so I thought i'd throw it out there to you guys. You can see the stamped markings, but on the copper around the spring are the letters FBGZ.
It would be great to find the brand and get one in a 80C. Thanks for the help.

 

Could be a Stant. Try part number 13868 (180°) or 13869 (195°). $6 at Advance Auto Parts.

--Ferdi

 

All the Stant's I've seen say Stant on them. I've had a Stant side by side with this one and this one's a superior design.

 

Stant has two different versions with the 'regular' being superior to their 'superstat'. There was a thread about on miata.net like 10 years ago. The regular one looks just like the one you pictured with the bigger diameter opening that actually also opens further compared to the superstat. Just go down to Advance and check it out.

--Ferdi

 

or watch Joe Perez's Amazing Video: