I'm no guru. Not versed on the multitrack machines. My guess on this is it is a Stephens multitrack?
Does not appear to have pinch rollers or capstan shafts. John Stephens was apparently a genius when it came to tape tension servo control
It does have a pinch roller on the capstan. It's actually an Australian made tape machine called an Optronix (Optro), I think the only multi track tape
machine ever made here. It's been sitting around for years but needs quite a bit of work. The mechanics are I believe very robust but electronics are
unknown. Restored to full working condition with upgraded electronics it would be a very good machine.
WRT pinch rollerless machines I think there were ATR-100/102 (1/4" 1/2") and ATR-124 24/16 track Ampex and the Stephens.
It seems there were very few Stephens machines made but people who have had them swear they are really great sounding, maybe
even the best.