I have never wondered this until it came up here. The way I learned when learning to work on power plants was that you just put the unit after the value. For instance, 450 F. The degree symbol was used after a number to indicate "rank". For instance, 1º and 2º meant primary and secondary, respectively. I suppose this is a more mathematical notation than a conversational one, since it was in reference to thermodynamics.
FWIW, I held down the option/alt key on my Apple laptop, and poked stuff until I got it. It ended being the zero key. I am still learning the Mac...and believe me; it is bad, since I suck on my PC too!