Two=part perpetual calender - has mouth disc fitting inside recess in base disc carrying numbers for days around edge

摘要

The perpetual calender made from two parts, has a base (1) shaped as a disc, with a circular depression (4) on top, holding a disc (5). The base disc carries the thirtyone numerals (3) for the days around its outer surface. The upper disc carries a set of twelve numbers (6) for the months, arranged as an incomplete circle. Adjacent to each number for a month is a depression (7) to hold an indicator (8). The edge (4a) of the upper disc incorporates a projection extending towards the inside vertical face of the recess forming a marking device. An alternative design uses a pointer rotating about the centre of the upper disc. The surface of the upper disc projects above the surface of the base disc.