Moonphase
Also called moon phase
A moonphase is a complication that shows the current phase of the moon, usually through a window where a disc with a moon image rotates.
It's largely decorative and popular on dress and calendar watches. Different designs vary in how accurately they track the lunar cycle before needing a correction.
When a moonphase watch has stopped, it may need its moon set against a reference before it's sold, which is worth doing so the watch presents correctly.
The moon disc can also fade or be damaged, and replacements aren't always easy to source for older watches, which affects value.
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