HP 21mx/whatever processor works with doublesided key... i forgot model#

[Ed via cctalk]

Progress!
 
HP 21mx/whatever   processor   works  with double  sided  key... (I forgot 
model#)
 
Thank goodness  for that  guy ion  ebay selling them!
 
 I  got  2... one to use...and  one  to   loose/put in bag of keys.
 
Now  to replace the   fuse holder on the back... that  is  mushed.
 
It has ... of all things  3  tty  boards in it? what  is  with that? Multi 
user without  a  mux?
 
Has  2  memory boards   think I  remember   64k total.
 
need to  find a  paper tape  basic   to   play  with.
 
Any other  advice?
 
Ed#