Caliber JJ04

Christopher Ward's moonphase module, on a Sellita SW220-1. The house's page says the base's date wheel and its spring-loaded assembly are taken out and replaced by four wheels that drive the moon disc, with two more for setting it, and that the display follows the moon accurately for 128 years. Many moonphases advance once a day in a single step; this one moves the disc continuously, so the moon never sits still between jumps. The page gives 26 jewels, 4 Hz and 38 hours.