Japanese Watch Listing Service Terms: OH済, 要OH and 研磨 (2026)

A Japanese pre-owned watch listing usually carries a short block of text about service and finishing that decides two things a buyer abroad cares about most: how soon you will need to spend money on the movement, and whether the case still looks the way the factory made it. These Japanese watch listing service terms — OH済, 分解掃除, 要OH, 研磨, 未研磨 — are written in shorthand that the machine translation from a copy-paste rarely captures the way a collector reads them.

This guide translates that block term by term, tells you which words move value and which are just noise, and shows you how to read a real listing line by line. It is written for buyers outside Japan who cannot walk into the shop and ask. Everything here is current as of September 2026, and the maintenance figures cite each manufacturer or a dated industry source so you can confirm them yourself.

Two ideas run through the whole article. First, a service word without a date is almost meaningless — “OH済” (overhauled) tells you nothing until you know when. Second, on the case, less is more: an unpolished watch is generally worth more than a polished one, because metal that is buffed away never comes back.

Japanese watch listing service terms, in 30 seconds

Before the detail, here is the short version. The service line answers “what will the movement cost me soon?” and the finish line answers “is the case original?” Read both with a date attached.

• OH済 (overhaul done) — the movement was fully serviced. Only useful with a year and, ideally, who did it.
• 分解掃除 (disassembly cleaning) — the same thing as an overhaul; older shops and Seiko service slips use this phrase.
• 要OH / OH推奨 (overhaul needed / recommended) — budget for a service on top of the purchase price.
• 研磨 (polished) vs 未研磨 (unpolished) — unpolished usually commands a premium, especially on vintage.
• 日差 (daily rate) — the seller’s measured accuracy in seconds per day, e.g. “日差+5秒.”

Definition: an overhaul (Japanese: オーバーホール, abbreviated OH) is a full service in which the movement is completely disassembled, cleaned, re-lubricated, reassembled, regulated for accuracy, and fitted with fresh gaskets — not a battery change or a quick tune. That is the single term the rest of the listing revolves around.

What “OH済” actually means — and what it doesn’t

“OH済” (済 = completed) tells you a full service was performed. It does not tell you when, by whom, or whether any parts were replaced with non-original ones. Those three gaps are exactly where a buyer abroad gets caught, because you cannot ask across a screen as easily as a walk-in customer can.

OH済 vs 分解掃除 vs 要OH

Japanese sellers use several phrases for the same underlying work. The table below is the vocabulary you will actually meet on Yahoo Auctions, Mercari and dealer sites, with what each one should make you do.

Japanese	Reading / literal	What it means	What to do
OH済 / OH済み	オーバーホール済 (overhaul done)	Movement fully serviced	Ask for the year and who did it
分解掃除 / 分解掃除済	bunkai sōji (disassembly cleaning)	Same as an overhaul (older term)	Treat identically to OH済
OH歴あり	overhaul history exists	Serviced at some point in the past	Vaguer than OH済 — pin down the date
要OH / OH推奨	overhaul needed / recommended	Not recently serviced; service advised	Add a service to your budget
未OH / 未整備	not overhauled / not serviced	Sold as-is, no recent service	Assume a full service is due
稼働品 / 稼働確認済	working / operation confirmed	It runs — not that it keeps good time	Ask for a measured daily rate
電池交換済	battery replaced	Quartz: fresh battery only, not an OH	Do not read as a movement service

Who did the overhaul matters as much as the date

An overhaul is only as good as the watchmaker and the parts. Japanese listings usually flag this, and the distinction is worth reading carefully:

• メーカーOH / 正規OH — manufacturer or authorized service. The service slip may extend a service warranty; original parts.
• 一般時計店OH / 時計技師OH — independent watchmaker. Often competent and cheaper, but parts and finishing vary; some brands will not honor later work if non-original parts were fitted.

Ask for the service invoice (明細 / 作業伝票). A dated invoice that names the servicer is far stronger evidence than the words “OH済” in a description. When RYUZU WATCHES inspects a watch before you pay, this is one of the documents we check and photograph.

How often each brand actually needs an overhaul

This is why the date on “OH済” matters so much. A listing that reads “OH済 2019” in a 2026 sale is not “recently serviced” for most brands — it is already inside, or past, the recommended interval. The figures below are the manufacturers’ own general recommendations; real-world need varies with use, and quartz servicing is lighter than mechanical.

Brand / type	Recommended overhaul interval	Source (dated)
Rolex (modern)	About every 10 years (roughly 8–10)	Rolex recommendation, reported Sept 2026
Rolex (vintage, pre-1980s)	Every 5–7 years	Industry guidance, Sept 2026
Omega (mechanical)	Complete service every 5–8 years; water-resistance check yearly	Omega official FAQ
Grand Seiko (9S mechanical)	Overhaul every 3–5 years	Chronos Japan, citing GS guidance
Grand Seiko / Seiko (9F quartz)	Overhaul roughly every 4 years	Chronos Japan, citing GS guidance

Two practical reads follow from this. First, translate the stated service year into “years remaining” for that specific brand before you value the listing. Second, treat “稼働品” (working) and “OH済” as different claims: a watch can run and still be years overdue for a service. For what an overdue service actually costs once the watch reaches you, see our guide to Grand Seiko and Seiko service costs from abroad.

Polishing: 研磨, 未研磨, 純正仕上げ — the term that moves value most

If one line in the finish block deserves your full attention, it is polishing. Unlike a service, which can be redone forever, polishing removes metal that can never be put back. That is why Japanese collectors and dealers call out the case finish so precisely.

What polishing removes

A factory case has sharp lug edges, crisp bevels (chamfers), clean lug holes and defined transitions between brushed and polished surfaces. Buffing to remove scratches softens all of that. According to a dated industry guide (September 2026), a typical case can be meaningfully refinished only about five times before those lines are lost, and over-polishing shows up as rounded lugs, faint or missing bevels, blurred bezel engraving and a visibly thinner case.

The unpolished premium

Original metal cannot be restored, so collectors pay more for it. The same industry guide reports that over-polishing can cut a vintage watch’s value by roughly 5–20% on its own, while overall condition grading can swing the final price of two otherwise identical references by 30–50%; on highly collectible pieces the penalty for a tired, over-polished case is steeper still. These are reported ranges from one source as of September 2026, not guarantees — but the direction is consistent across the market: 未研磨 (unpolished) generally sells for more than 研磨済 (polished).

The finish vocabulary, and one word to watch

Japanese	Reading	Meaning
未研磨	mi-kenma (unpolished)	Case never re-polished — usually the premium state
研磨あり / 研磨済 / ポリッシュ済	polished	Case has been buffed at least once
ケース研磨済	case polished	Specifically the case was polished
純正仕上げ / 純正研磨	original / factory finish	See caution below
社外研磨	third-party polish	Polished outside the maker — finish quality varies
ヘアライン仕上げ	hairline / brushed finish	Brushed surface preserved (not mirror-buffed)

Caution on “純正仕上げ” (original finish). This phrase is ambiguous. It can mean the case still wears its untouched factory finish — the best case — or that a shop re-finished it back to a factory-style spec, which is still a polish. Ask which one is meant, and request sharp photos of the lugs and bevels at an angle so you can judge for yourself. On a screen, the geometry of the edges tells you more than the seller’s adjective.

Worked example: reading a real service-and-finish block

Here is a service-and-finish line of the kind you will see on a Japanese dealer listing, followed by a line-by-line translation. Suppose the sale is dated 2026 and the block reads:

2019年メーカーOH済、その後稼働良好、日差+5秒、未研磨・純正仕上げ、パッキン交換済・簡易防水検査済。

1. 2019年メーカーOH済 — “Manufacturer overhaul completed in 2019.” Good provenance, but seven years old at a 2026 sale. For a modern Rolex that is mid-interval; for a Grand Seiko 9S it is already past the 3–5 year window — budget for a service soon.
2. その後稼働良好 — “Running well since.” Reassuring but subjective; pair it with the daily rate below.
3. 日差+5秒 — “Accuracy +5 seconds per day.” A measured figure, which is stronger than “working.” Within spec for most mechanical watches.
4. 未研磨・純正仕上げ — “Unpolished, original finish.” The value-positive combination — but confirm whether “original finish” means untouched or re-finished (see the caution above).
5. パッキン交換済・簡易防水検査済 — “Gaskets replaced, simple water-resistance test done.” A “simple” test is a pressure check, not a guarantee — do not swim with a pre-owned watch on the strength of it.

Read that way, the block is genuinely informative: authentic manufacturer service history, a real accuracy figure, and an unpolished case — with one item (“original finish”) to clarify and one service that may be due depending on the brand. For the rest of a listing — box, papers and spare links — see our guide to reading full-set and head-only terms on a Japanese listing.

What an “OH済” listing does not guarantee

A clean service line raises confidence, but it is not a substitute for authentication, and the words carry marketing weight that the facts may not support. Keep these separate in your head:

• Serviced is not the same as genuine. An overhaul confirms the movement was worked on, not that the watch is authentic or that every part is original. Authenticity is a separate check — see how to authenticate a watch when buying from Japan.
• Authentic is not the same as authorized. A pre-owned watch bought from Japan’s independent market is typically authentic (genuine), but it is not authorized-dealer stock and carries no brand certification. Do not read “OH済” as a factory endorsement.
• A service warranty is not a manufacturer warranty. An independent watchmaker’s work may carry a short shop warranty, which is not the brand’s international guarantee and may not be honored abroad.
• “Original parts” needs evidence. If originality matters to you, the service invoice should say so; the word “OH済” alone does not.

A pre-purchase checklist

Before you commit to a Japan-sourced watch on the strength of its service and finish line, confirm the following:

• ☑ Get the overhaul year, not just “OH済.” Convert it to years-remaining for that brand’s interval.
• ☑ Ask who serviced it — manufacturer/authorized or independent — and request the dated invoice (明細 / 作業伝票).
• ☑ Get a measured daily rate (日差), not just “稼働品” (working).
• ☑ Confirm polished vs unpolished, and if “純正仕上げ” appears, ask whether it means untouched or re-finished.
• ☑ Request angled photos of the lugs and bevels to judge the case geometry yourself.
• ☑ Read “simple water-resistance test” as a caution, not a clearance to get the watch wet.
• ☑ Budget for a service if the interval has lapsed — factor it into your landed cost.

Frequently asked questions

Does “OH済” mean I won’t need to service the watch?

No. It means the watch was serviced at some past date. Whether you need another service depends on how long ago that was and the brand’s interval — for example, roughly 10 years for a modern Rolex but 3–5 years for a Grand Seiko 9S. Always convert the stated year into years-remaining.

Is an unpolished watch always worth more?

Generally yes, especially for vintage pieces, because polishing permanently removes metal and softens the factory lines. One dated industry source (September 2026) puts the value hit from over-polishing at roughly 5–20% on vintage watches. The exact premium varies by reference and overall condition.

What is the difference between OH and 分解掃除?

They describe the same work: a full disassembly, cleaning, re-lubrication, reassembly and regulation of the movement. “分解掃除” (disassembly cleaning) is the older, more literal phrase and appears often on Seiko-related service slips; “OH” (overhaul) is the common shorthand. Treat them identically.

Should I trust an overhaul by an independent watchmaker?

Often, yes — many independents do excellent work at lower cost. The things to verify are the parts (original vs generic) and whether the brand will still honor future service if non-original parts were fitted. Ask for the dated invoice and, where originality matters, confirm original parts were used.

How do I know if a case was polished if the listing doesn’t say?

Ask directly, and request sharp, angled photos of the lugs, bevels and lug holes. Rounded edges, faint or missing chamfers, blurred bezel engraving and a thin-looking case are the signs of past polishing. On a screen the edge geometry is more reliable than any adjective the seller uses.

Key takeaways

• A service word needs a date. “OH済” only helps once you know the year and can compare it to the brand’s interval.
• 分解掃除 = overhaul; 要OH = budget for one. Learn the handful of shorthand terms and what each one costs you.
• Unpolished (未研磨) usually beats polished. Metal removed by buffing never returns; the value gap is real, especially on vintage.
• Who serviced it, and with what parts, matters. Ask for the dated invoice; manufacturer service and independent service are not the same claim.
• Serviced ≠ genuine ≠ authorized. A clean service line is not authentication and not a brand warranty.

If you have found a specific reference in Japan and want the service history, finish and parts checked before you pay, RYUZU WATCHES can search the Japanese market on your behalf and inspect the watch — including reading and photographing the service invoice and the case geometry — before you commit.

This article reflects manufacturer recommendations and market guidance as of September 2026. Service intervals are general recommendations that vary with use; value figures are reported ranges from the cited sources, not guarantees. Confirm current details with the manufacturer and the seller before purchase.