Plato armillary sphere - additional scales
In addition to the scales described in the Epact entry, there are some others worth noting.
The upper and lower edges of the equator are engraved. On the upper edge are 24 hours, divided to quarters and alternately cross-hatched. On the lower side the circle is divided into the zodiac signs with symbols, to correlate with the ecliptic.
On the meridian ring there is a scale from the equator to the Arctic circle from 1 - 24. The divisions become progressively more closely spaced. The position of 24 with the Arctic circle might make it seem that it correlates the maximum length of the day with latitude, but that cannot be correct as we would have 12 rather than 0 at the equator.