I have always been a great fan of Eurostile-Microgramma. I think 2001: A Space Odyssey had much to do in that matter. I don't know if it's the one used for eye-charts, but given it's "scientific" look it might appear to be.
And how can't you warm it up & and cool it off if your using FS? :)
I think Microgramma might have been designed with a square in mind, but it's curved glyphs where treated in a more grotesque-ish way. I imagine since they didn't have FS back then and Helvetica came into fashion, Eurostile's lc did not come squarish at all. So this is how FS modularity updates the concept for me. Glad you like it.