431.13.41.22.01.001Ref

The Annual Calendar is a great complication. While a regular mechanical calendar watch needs an adjustment on every month with less than 31 days, the Annual Calendar makes the 30-31 distinction and only needs an adjustment in February. It does not command the high prices of a perpetual calendar, while it is mechanically interesting and hardly less functional. The caliber 8601 is based on the wonderful 8500 and shares the same intricate finishing.