A clock with one winding hole that strikes the hour?

I comfortably walked into his living room and told the client "your clock is non-striking, so how can you complain that the striking isn't working? Here look, there is only one winding hole". The client then pointed to the bell, hidden at the back. I was in shock.

My reputation was no longer at risk, it had disappeared as fast as I had entered the room. The client then proceeded to explain that this Swiss Neuchâteloise clock only has one winding hole to achieve two things: it winds the clock and it winds the bell! But how? With only one winding hole?

Neuchâteloise clock

Only when I opened the clock, did I discover the sophistication and reliability of this Swiss design. A little toggle containing two wheels  will switch which train you are winding depending on whether you turn the winding key to the right or the left. See picture below. The toggle with the two wheels sits just below where the word Zenith appears. How ingenious!

the one winding hole toggle allowing you to wind two trains