This brass nocturnal consists of a range of scales, discs and indices. Attached to the main disc is a small handle in the shape of a pierced fleur-de-lis, inscribed with a pair of initials.
The FRONT of the MAIN DISC has a circular calendrical scale with the usual Latin names of the months, numbered 1 to 12 starting with January. Each month has the corresponding number of days (December has 311/4 to indicate the leap year). The centre of the handle corresponds to 24th October.
In the centre of this scale is a VOLVELLE with an hour scale, numbered anticlockwise 1 to 12 twice. Teeth of alternating size indicate the full and half hours. An index with a sun effigy at 12 o'clock allows this volvelle to be set to the correct date. The centre of the disc is engraved with scrollwork.
Over this volvelle rotates an INDEX ARM, marked around the central hole 'STELLA POLARIS' and along the arm 'INDEX HORA NOCTIS'. The signature of the maker is inscribed on the same arm.
The REVERSE is inscribed with several circular scales as follows (from the outside):
1) a degree scale 0° to 360°.
2) a 24 hour scale, numbered clockwise 1 to 12 twice.
3) a compass rose of 32 points, with the eight cardinal points shown by their first letter(s), North indicated by a fleur-de-lis.
In the centre of this scale is a fixed DISC inscribed with the age of the moon from 1 to 30.
Over this disc rotates a VOLVELLE with an index. A circular aperture shows the phases of the moon. The plate is marked with planetary aspects but has not been completed.
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