The button is the power reserve indicator. When you push it, the seconds hand jumps forward a certain amount depending on how much power is left in the capacitor. A fairly unique feature of Seiko kinetic watches as far as I know!
I use it daily. Mostly cooking, timing the kid's naps, tasks at work, etc. This Baltany has a 12 hour totalizer so I even time how long I sleep for when I feel like I'm not getting enough.
All things that could be done using my phone or a smart watch, but I really enjoy using my regular watches this way 🙂
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