The band with the world's most famous chronograph mouvement has more to offer the fusee chain is such a gorgeous complication and one not that many brands make I was told more than once it is more difficult to make than the overhyped tourbillon anyway, he...
The two tapered cones serve to "even out" the amount of torque so when the barrel is fully wound to when it is almost completely unwound, the same force is available - for better timekeeping. Great photos Bruno! Cazalea (from Wikipedia) ...