Wow, it's in beautiful condition. I've never heard of these, but it looks like a competitor to the RACAL 4DS.
If so, it's not really intended for use as a studio recorder, it's designed to record signals for experimentation. It should be able to record ultrasonics and probably subsonics via an FM recording system - whether it's actually good for recording music is anybody's guess, though.
Chances are it will not be able to play back tapes made on a regular machine, though 4DS instrumentation tapes might work.
what speeds can it do? The 4DS could go up to 60ips...