The disadvantage to a single pusher is that you cannot stop timing an event, pause, and then restart timing. The sequence is start, stop, and reset, and if you want to time successive intervals, you must stop the chronograph, write down or remember the elapsed time, reset the chronograph, and start it again. This crisis in modern civilization was not addressed until Willy Breitling’s patent of 1934, which was for a modern two-pusher design – the upper for start, stop, and restart, and the lower for reset-to-zero. The 20th century was a time of considerable innovation in chronograph design and produced some interesting mainstream innovations (the automatic chronograph, the cam-and-lever chronograph) as well as some rather oddball notions which have not stood the test of time, including a vertical clutch design consisting of a rubber clutch plate driven by another plate with teeth in it to grab the rubber, which has been, deservedly, consigned to the dustbin of history.