m90 thermostat question

Hi guys, I've been an e21 and e36 guy for the past few years (80 320is running a BAE turbo and a 98 328is). Last week my dad and I picked up a 79 635csi euro import. My dad has handed it off to me to fix a few things.

My question is were there different degree thermostats for the m90 motor? Because when this one is fully warmed up, the temp gauge on the cluster reads just above the blue.

here are a few pictures:

m90 thermostat question