Automatic, quartz, Spring Drive and Eco-Drive: Japanese movements explained
Every listing on Tokyo Time states its movement type, because it changes what the watch costs to own more than almost anything else about it. Here is what each one means in practice.
Automatic
A mainspring, wound by a rotor that turns as your wrist moves. Wear it and it runs; leave it in a drawer and it stops in a day or two, which is normal and not a fault. Expect somewhere between −20 and +40 seconds a day on a vintage Seiko, and considerably better on anything modern or recently regulated.
Needs a service every five to ten years. It will run without one for far longer, and doing so is how pivots get destroyed.
Hand-wound
The same thing without the rotor, so usually thinner and often better finished for the money — there is no rotor covering the movement. Wind it once a day. King Seiko's 44A and Seiko's Laurel-era calibres are hand-wound and are the reason those watches wear so well under a cuff.
Quartz
A battery drives a quartz crystal oscillating at 32,768 Hz. Accurate to around fifteen seconds a month as standard, and Seiko and Citizen both make thermocompensated versions accurate to five or ten seconds a year.
Japan launched the first one — the Seiko Astron, Christmas Day 1969 — and then very nearly destroyed the Swiss industry with it. A battery every two to five years, and a capacitor eventually. The thing to check on a vintage quartz is whether it has ever leaked.
Solar (Eco-Drive, Seiko Solar)
Quartz, charged by light through the dial into a rechargeable cell. No battery changes; the cell itself lasts perhaps ten to twenty years and is replaceable. Citizen's Eco-Drive is the best known and has been in production since 1995.
The thing to ask about a used one: does it hold a full charge? A tired cell shows up as a watch that stops after a few days in a drawer.
Kinetic
Seiko's answer to the same problem: quartz, charged by a rotor rather than by light. Elegant, and the capacitors in the older ones are a known weak point — many have already been replaced once. Check when.
Spring Drive
Grand Seiko's, and unlike anything else. A mainspring provides all the power — no battery — but instead of an escapement the rate is regulated electromagnetically by a quartz reference. The result is one second a day and a seconds hand that glides continuously rather than ticking.
Serviceable only by Seiko, and not cheap. Worth knowing before buying a used one out of warranty.
Digital
Casio's ground. A quartz oscillator and an LCD, and in the case of the G-Shock a module that will outlive most of the people reading this. Battery every two to ten years depending on the model.
Which to buy
There is no correct answer and the honest version is that it depends what you want from it. A vintage automatic is a mechanical object with a service bill. A solar quartz is a watch you will never think about again. Both are legitimate, and the comparison people make between them is usually about something other than timekeeping.
Tokyo Time is a classifieds site, not a dealer or a valuer. Nothing here is an appraisal of any particular watch.