Correct RD, at least as manufactured. A concave surface to match the arc of travel and pick up on the ball is the ideal. Don't forget that little bit of free play for you folks with pushrods that wear. That's my take on it, works for me.
So Brandis can get some respite, here is the rest of the story.
These engines have a timed breather, in other words the crankcase is only open to atmosphere when pistons are in a certain position. The breather duct runs across the crankcase, exiting above the gearbox sprocket. Late engines it's just a hole, earlier engines originally had an extension tube down to the sump plate, late plunger bikes the tube is short, oil mist directed onto the chain.
Now the clever bit. The peg on the cam gear locates into the breather bush, which looks like a top hat. This bush rotates in the inner timing cover, opening and closing the drilling which connects to the breather duct. The peg drives the bush, so everything is timed up back to the crank. The cork washer keeps the breather bush against the timing cover and acts as a seal so that oil mist can only enter the breather via the small hole on the outer end. Breather bush, cork washer and cam gear rotate as one.
From the description of a steel face it sounds as if the bush is seized solid, and it will take every trick and skill to free it off without damage. The bush changed slightly over time, but the set up is the same as on later engines and there are plenty of pictures and viddys on the web.
Swarfy.
