In looking that thing over it appears to be gear reduction but mentions direct drive .I would assume it's basically a 6-10 .
What would make it special is the third semi closed transfer tunnel much like the early 10-10s which was later only two tunnels on the 700's .
I'm going to delve into it after I get things back in order from having a bunch of hardwood layed down for flooring .House is in a shambles at the moment .