Japanese watch glossary

GLOSSARY

Movements & technology

movement (calibre · caliber)

The engine of the watch — the mechanism that keeps time and drives the hands. Identified by a calibre code (e.g. Seiko's NH35). Mechanical, quartz, solar and Spring Drive are all movement families.

mechanical movement (automatic movement)

A movement powered by a wound spring rather than a battery. "Automatic" means a rotor winds it as you move your wrist; "hand-wound" means you wind the crown yourself.

quartz

A battery-powered movement regulated by a vibrating quartz crystal — the technology Seiko commercialised with the Astron in 1969. Generally more accurate than mechanical and far less costly to run.

Spring Drive

Seiko/Grand Seiko's hybrid: a mainspring provides the power (like a mechanical) while an electronic regulator disciplines the rate — giving the signature gliding seconds hand.

solar movement (Eco-Drive · Tough Solar)

Quartz powered by a light-charged cell instead of a disposable battery. Citizen calls it Eco-Drive; Casio calls it Tough Solar. Years of service with no battery swaps.

hacking seconds

When pulling the crown out stops the seconds hand, so you can set the time to the second. Some budget movements (like Seiko's 7S26) famously lack it.

power reserve

How long a fully wound mechanical watch runs before stopping. The official figure is on the maker's spec sheet — we quote it from there, never from hearsay.

accuracy rating

The maker's stated rate band, e.g. seconds per day (mechanical) or seconds per month/year (quartz). A published spec, not a promise for any individual watch.

Case, dial & sizing

lug-to-lug (L2L)

The full length of the watch from the tip of the top lugs to the tip of the bottom lugs. The single most useful fit number: enthusiasts agree it should stay within the flat top of your wrist. See /fit.

case diameter

The width of the case in millimetres, usually excluding the crown. Useful, but it says less about fit than lug-to-lug and case shape do.

lug width

The gap between the lugs in millimetres — the strap size you need (e.g. 20 mm). Even numbers are easiest to find straps for.

lume (LumiBrite · luminous paint)

The photoluminescent paint on hands and markers that glows after light exposure. Seiko's compound is LumiBrite. A "lume shot" is the enthusiast ritual photo in the dark — this site's dark theme is one.

zaratsu polishing (zaratsu)

The blade-polishing technique associated with Grand Seiko: cases finished against a rotating tin plate to produce distortion-free mirror surfaces between crisp lines.

water resistance

The tested static rating (e.g. 10 bar / 100 m). Ratings are about pressure, not literal swim depth — dedicated dive watches follow the ISO dive standard; low-rated dress watches should stay dry.

sapphire crystal (Hardlex)

The glass over the dial. Sapphire is the most scratch-resistant common option; Seiko's Hardlex is a hardened mineral glass used across its accessible lines.

The Japanese market

JDM (Japan domestic market)

Japan-domestic-market: models, dials or editions sold officially only in Japan. A structural layer of Japanese watchmaking — and the coverage this site exists for.

reference number (model code · ref.)

The maker's exact model code, e.g. SKX007 or SBGA211. The precise way to talk about a watch — one model name can span many references with different dials, sizes and regions.

kanji day wheel

A day-of-week disc printed in kanji (often paired with English). A JDM detail collectors seek out on Japanese-market references.

boutique edition (shop-limited edition)

A model limited to a brand's own boutiques or a specific retailer — in Japan, often a Ginza or Nihonbashi flagship. Documented in the official release announcement.

Seiko mod (modding)

The culture of customising affordable Seiko watches (dials, hands, bezels) around widely available movements like the NH35/NH36. Changes the watch from original spec — a hobby, not a manufacturer program.

Buying & ownership

authorized dealer (AD)

A retailer officially appointed by the brand. Purchases come with the manufacturer's warranty as issued at sale. The alternative — the grey market — is legal but warranty terms differ; know which you're buying from.

grey market

Genuine watches sold outside the brand's authorized network, often at lower prices. Not counterfeit — but manufacturer warranty coverage and return terms differ from an AD purchase. We explain the trade-offs neutrally; check the seller's own terms.

proxy buying (proxy service)

Using a forwarding/purchase service to buy items only sold within Japan (JDM releases, domestic listings). Adds fees and shipping steps — our buying guides walk through how it works.

service interval

How often a mechanical movement should be professionally serviced. Makers publish recommendations; actual need varies with use and the movement — we cite the maker's guidance, not folklore.

price as-of date (price_as_of)

Every price on this site is a dated snapshot — the day we verified it — never a live quote. Prices and stock change; the retailer's page is always the current truth.