Twin chrono for ability to time two events and the difference in time between them.
Two individual timed chronographs at the bottom subdials with a third register acting as a split-second differential at the upper subdial. It’s a monophsher: The first push starts the two bottom subdials where they begin timing. The second push stops the dial on the lower left and begins the split-recording dial on the upper subdial. The third push stops the second time (lower right) and the split time (upper). The fourth and final push brings everything back to zero.
All three of the subdials have both minute and seconds and hands in contrasting red and white, so timing can be hours long.
Designed for yacht racing matches; I will never need it for this type of event 😀