On Mon, Jan 25, 2016 at 2:54 PM, Paul Berger <phb.hfx at gmail.com> wrote:
  These tapes where used in a number of machine such as
9825, 9831, 9835,
 9845, 9915, and 85A&B. 
And the HP 9815 desktop calculator, 2644 terminal, 4951A protocol
analyzer. Probably other products as well.
   There was also at least 1 external tape drive that
 used these tapes 
HP 9875 dual, 9877 quad
  not to mention DEC made a drive for them as well.
The DEC TU58 drive uses the same physical cartridge (DC100), but can't
read HP formatted tapes, or vice versa.