An extremely rare pre balance spring English silver pair case Astronomical verge watch with year calendar indicating date, month, sign of the Zodiac and time of sunrise with further indications for day of the week, and the age and aspect of the moon, signed “Henricus Harpur / Londini”, circa 1670, 55 mm diam

calendar

The calendar is a self contained unit pinned by means of three feet to the top plate. All the wheel work is fitted into recesses within the calendar plate. A six leaf lantern pinon on the fusee arbor engages the hour wheel [30] which, in turn, has a lantern pinion of four leaves driving the day of the week wheel [56].

The 13-leaf pinon on the day wheel engages all three remaining wheels.

These are the moon disc [59] and two superimposed wheels [60 & 62] which carry, respectively, the Zodiac disc and month hand. These latter two wheels are held together by tension washers which permit them to slip past each other and move at different rates causing the hand to progress through the month sectors engraved on the disc.