Was there anyone of iconic status in the world of style - actor, president, nobleman, etc. - who regularly wore the kind of three-button that Amies was talking about (the "2 and a half", where the top button could be buttoned, but it's not supposed to be)? I'd love to see how it "really should" fit.
I bet you'd find loads from the golden age of the three button - about 1960-1965. Terence Stamp? Michael Caine? (he has a nice suit on when he gets out of prison n 'The Italian Job' which was 1969), Belmondo, Delon, Steve Marriott? Bowie? Jagger? Watts?