I was able to get Krause on the phone today, and John in parts was very helpful. He identified it as a model 311, from 1960-to-1965 year.
He identified it has having 1 1/8" diamter, round tie rod or gang bolt.
So let me get this straight -- a round axle with round holes in the disc blades --- do they free-wheel spin on a round axle ? Or does the tightened tension against the spacers & end washers not let them free-wheel ?