<There was a TRS-80 model 1 Zork that meets this description -- I bought
<it years ago. It was a single-density disk (The model 1 used a 1771
<controller that could only do single desnity), and it was formatted
<strangely 'copy protect' it. It was also a self-booting disk with no
<filesystem as such -- the Zork program just read the text (encrypted
<IIRC) from raw sectors on the disk.
I think the trs80 boot code loaded on a few sectors that acutally booted
and loaded ZORK as there were other things in the way of odd skewing and
sector numbering the standard code didn't like.
<Superutility on a TRS-80 could probably read/back up that disk, but I
<don't know what else can.
Or suprzap (or several others) on one of many systems using the older 1771
controller (S100, Bigboards and others).
Allison