thetypewriterman wrote:

Re; Typeface and typefaces.  My understanding has always been that the singular is a 'typeface', but when referring to all the type in the segment, you also say 'typeface' - as in 'The typeface on that machine is dirty'. (meaning all them not just the one).

I have never encountered that meaning of "typeface" and it seems pretty awkward to use it that way. For one thing, the word "typeface" properly means the design, the style, of the characters and not their physical being. For another, it is the slugs that are dirty in your example and we refer to the slugs in the plural... I think the whole thing is just an idiosyncratic usage that you heard and not normal usage and you might as well forget about it.