It was missing. An original one was available, but too short. A proper one was to make by hand. This one is hardened and rough finished. The pins between the hairspring works are still missing. The details will be completed when the hairspring is fit to the balance and every part finished. The distance, middle pins to the balance center is to take from the available hairspring its terminal curve close to the cock edge.

Later I saw that also the terminal curve of the balance spring was altered. Thus I made a second index because the pins must be in the correct position to the terminal curve. Look under 12th May.