[texhax] ?encoding? suffices in the TeX Live Adobe font TFMs

[Karl Berry]

    I see (for example) 7t, 8c, 8r, 8t, 8y and

http://www.tex.ac.uk/tex-archive/info/fontname/html/Variants.html
It is certainly far from perfect or complete or authoritative, but it
is I can point you at today.

There are no links to .enc or .etx files for these in the document,
although I believe some exist, in particular font packages (Latin
Modern, Inconsolata).  I know that is vague and imprecise but it's what
I have to offer.  Sorry.

    even an 8rn, 

8r is the encoding.  n is the width (narrow).

    a reference to an authoritative document
    describing these ?

Everyone makes their own decisions, so nothing is authoritative.
That's the reality.