On 10/16/18, William Pechter <pechter at gmail.com> wrote:
  DEC Tape II was the serial driven TU58.
 The TK50 was CompacTape or something like that.  It was the predecessor of a
 number of square tapes...
 See DLT on Wikipedia 
https://en.m.wikipedia.org/wiki/Digital_Linear_Tape
 My mistake.  Yes, I was thinking of the TU58, a most miserable device.
-Paul W.