Some sort of closed-captioning equipment; the disk
itself was created by
Svensk Text AB in Stockholm, probably during the 1980s.
I've found the Swedish Teletext chracter set assignement but it simply
re-assignbes a few of the normal ASCII codes, licluding []{}. I can
attempt to give a representation of it, but as it doesn't use any prefix
characters, I don't think it's relevant.
-tony