The Avenir family that ships with Mac OS X comes with twelve faces. Avenir Book and Avenir Roman both have 400 weight, normal font-stretch, and are not italicized.
I'm building a product that lets users write text in custom fonts that they upload. Is there a standard way to determine which font in a family should be used by default? Is there some kind of setting in the fonts themselves that I'm missing that would tell me that?