Complication
Power Reserve Indicator
A fuel gauge for the mainspring.
What it does
Shows how much stored energy remains before the watch stops, usually as a small arc-and-hand gauge. It's most useful on hand-wound and less-worn automatics, telling you when a wind is due.
How to read it
Full means recently wound (e.g. 70 hours); as the mainspring unwinds the hand falls toward empty. Wind (or wear) before it hits zero to keep good timekeeping.
Impact on value
Slightly positive; a practical and elegant addition, common on Grand Seiko and haute pieces.
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Chimes the time on demand, to the minute.