Perhaps it is a common design but I've worked on a bunch of Tange, Shimano and similar headsets since the mid-'80's and never came across this particular design with it's lockring.

As to the toothed ring, I have a Tange headset on an late-'80's Trek that has the same toothed ring that engages matching teeth in the top race of the headset just like that shown in the picture above. The ring is not threaded but has an internal tab that goes into the vertical keyway in the fork steerer. The tab keeps it from rotating but it is removed by pulling it straight up.