As I've been looking into a first purchase I keep seeing pics of watch backs with the covers off. My question is what is the, I assume adjustment, that has a needle between F & S with a few tick marks?
I also have been looking to buy something that was perviously owned by prohibition era gangsters, esp. Al Capone, and was looking last night and came upon this. Now my birthday just passed so I would gratiously accept this as a late present! LOL