My guess the teeth are designed to go with a center pull brake cable stop (which is missing from your photos).



It helps keep the cable stop straight ahead. I haven't disassembled yet so I don't know if the cable stop & fork are keyed or not.

Ok.. so this is not the cleanest looking headset in the world. The bike still needs a good cleaning.

As far as the split crown race, that just looks odd. Usually the crown race seat is raised slightly. It would be a pain to install the crown race if the steer tube was straight to the bottom. But, the crown race takes a lot of impact from riding. The bike is reasonably ridable without a perfectly smooth crown race, but I'd think an unnecessary split would be a major wear spot.