A worm gear massively simplifies clock gear reduction for a simple two-handed case like this, totalling 5 gears. The worm to 20 tooth gear generates a 1/20 reduction, then the 8 tooth to 24 tooth on the differential is another 1/3 reduction, giving 1/60. The differential allows the main axle to run through to the large hand whilst constraining the small hand in position in the middle.
