I created a rendering which shows the exploded view of the base of the panoramic head. I wanted to sketch up the head to see if I could find a way for the detent indexing pin to work properly. There is a needle bearing between the upper and lower disks. I drilled out small holes on the inner washer every 30 degrees which allow the ball detent spring to index against. There is another small pin to locate the washer and prevent it from spinning inside.
Here is another view with "see through" enabled on the model, which may or may not make things clearer.