I can think of
the Commodore 64- 1541 drive
         
 Um, that wasn't any relative of RS422, RS423, RS232 or anything akin
       
  No, but it most certainly was a bit-serial interface. 
  Serial, yes,
but async, no.  It had a CLK and DATA line, plus an ATN line. 
 
True enough..
 Many people say it's just a serial version of the IEEE protcol, and I
 guess you could call it that, but it's somewhat inconsistent, in my
 opinion.  It has a dedicated ATN line, but many of the other signal
 lines are "emulated" by various sequences of CLK/DATA transitions. 
HPIL is perhaps closer to a 'serial IEEE-488 interface'. Althougb
electrically very different (it's not a bus, it's aloop, each peripehral
passes the data on to the enxt one), logically almost all concepts
transfer between the 2 intefaces. To the extent that for many
applications the HP82169 HPIL-HPIB translator is truely 'plug and play'.
-tony