Compax

Confirm the calendar and moonphase actually function before anything else

A complete calendar with moonphase is mechanically demanding and frequently non-functional on survivors, and non-functioning complications are sometimes concealed by fixing the discs in a plausible position. Set the watch through a full cycle: the day, month, date and moon should advance correctly and together. A calendar that does not move is a service question; one that moves incorrectly may indicate a movement assembled from parts of different calibers.

Calendar apertures multiply the opportunities for a redial to go wrong

A Tri-Compax dial carries more printed information than almost anything else of its era: two apertures, a pointer-date ring, register scales, a moonphase opening and the signature. A refinisher has to get all of it right, and the aperture edges and the moonphase opening are where the work usually shows — apertures very slightly the wrong size or position, printing that crosses a boundary it should not. Examine the apertures before the signature.