The regulating is always maked thanks to a needle that permits to adjust the size of the opening of oil out-flow.
The opening of the drip is the liminous zone in the middle of the piece. The black zone is the leather joint..
The free space let by the needle in the opening fixes the debit of the drip..
In closed position the needle obstructs the opening completely. It can be gotten quickly with the help of the lever to two positions situated in top of the mechanism.