QOTD: What Do You Know About External “Drum” Thermometers?

CC reader Donny B sent the following question:

I recently discovered that luxury vehicles from the 1970’s had “drum” style thermometers on the driver-side mirror. When did these disappear? I’d like to know because having one made late enough to use Celsius would be really cool, if such a thing exists. I don’t know where else I’d ask a question like this. Sometimes being a Canadian in half-Metric half-Imperial limbo is hard.

I’m sure the CC Cognoscenti will be able to help you out.