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

[Philip TAYLOR]

Forced to look (for the very first time) at
the TeX Live naming scheme for the TFM files
for the standard 35 Adobe/PostScript fonts,
I am puzzled by many of the ?encoding? suffices.

I see (for example) 7t, 8c, 8r, 8t, 8y and
even an 8rn, but looking (also for the first
time) at :

	http://www.tex.ac.uk/tex-archive/info/fontname/html/Encodings.html#Encodings

only "8r: TeX base" of the above 6 ?encoding?
suffices.  Could someone please enlighten me
as to the meaning of the other five (and of
any I may have missed), and also let me have
a reference to an authoritative document
describing these ?

Many thanks in advance :
Philip Taylor