drawing abbreviation
 

drawing abbreviation
i've run across an abbreviation on a drawing that i've never seen before. the drawing is an older drawing of structural steel. a dimension followed by "a.f" is next to the face of a bracket that is welded to the structure leg. what does the "a.f." mean? i cannot find reference to it in any drafting book, nor has my drafter heard of it. also, is there a book or document that summarizes typical drafting terminology?
there is old mil std 12 which lists most abbreviations, but i would guess this is after finishing or such.
above floor?