How we source numbers
Every number on the site is a fact copied from a named document, with where in the document it sits and the day it was checked. Makers’ documents lead; anything else is labelled; nothing is averaged or guessed.
What a fact is
The reference stores 5,357 facts in its entity files, plus 5,491 rows from makers’ tables (Seiko’s calibre and battery chart, Citizen’s and Casio’s model tables). Each fact keeps:
| Field | What it holds |
|---|---|
| Value and unit | The number as the document prints it, in its own unit: 53°, 10 bar, 21,600 bph. |
| Source | An entry in our register of documents: publisher, title, address, type, the day we opened it. |
| Place | Where in the document: page, table, section or drawing view. |
| Quote | The few words the number was read from, so anyone can find it again. |
| Checked | The day the fact was last read against its document. |
| Provenance | What kind of source it is (next section). |
The dates you see on a page, “Sources checked”, are the newest check among the facts that page prints. The newest check in the data is .
Provenance labels
Next to a number, a small label says what kind of source it comes from. Makers’ numbers carry no label, since that is the default. The share is of all facts in the entity files today.
| Label | Meaning | Share |
|---|---|---|
| manufacturer | A document from the maker: datasheet, spec sheet, technical drawing, manual or product page. | 83.2% |
| secondary source | A reference site that does not cite a primary document. Shown, labelled, not counted toward a page’s threshold. | 9.5% |
| seller listing | A parts seller’s guide or listing, used where makers publish nothing. | 4.1% |
| derived | Worked out by us from other facts, such as a difference between two sizes. It inherits the label of what it was worked out from. | 1.8% |
| measured | Measured on a real watch, by us, a reviewer or a retailer. The page says who. | 1.4% |
| owner reports | Owners’ reports and forum threads. Shown, labelled, not counted toward a page’s threshold. | 0.1% |
Which source leads
When several facts describe the same field, the page leads with the first in this order:
- The maker’s own document.
- Our own measurement.
- A reviewer’s measurement.
- A retailer’s measurement.
- A parts seller’s listing or guide.
- A secondary reference site.
- Owners’ reports.
A number we worked out ranks just after the source it was worked out from. Only the first five count when we decide whether a page has enough to stand on; secondary and owner sources are shown, labelled, but never carry a page alone.
When sources disagree
We keep every value and show them side by side; we never average. Sizes from a maker and from a measured review often differ by 0.3–1 mm. This is how it looks, live from the data:
The leading value comes first, then the others with their labels and footnotes. Tools that decide whether something fits use the less favourable value and say that the sources disagree.
“Not published”
A field reads “not published” when no document we have states it. We do not fill gaps with typical values or with the number of a sister model, and we do not stretch a number to variants the document does not name. Where we know why a value is missing, the page says so, for example “not published by Seiko”.
“Not applicable” is different: a mechanical watch has no battery, and a Casio digital has no case code. Those fields count as answered.
When a page is published
A page exists only when the data can answer its question, and is offered to search engines only when it can answer it well. The rules are fixed in code and the sitemap uses the same rules:
| Page | Exists when | Listed for search when |
|---|---|---|
| Battery size | Size and chemistry come from the cell maker’s datasheet. | At least 2 other codes and 2 movements or models use it, or people search for the code often. |
| Movement | At least 6 of its 14 key fields are sourced. | At least 8 key fields, and a watch in the data uses it or people search for it. |
| Watch model | At least 5 of its 10 key fields are sourced. | Its movement and at least 3 sizes are sourced. |
Key fields differ by kind: a mechanical movement is judged on lift angle and hand holes, a quartz movement on its battery, a Casio module on its functions.
Sizes and wrist fit
- Lug to lug is the straight distance between the lug tips. Casio publishes a case length instead (the L of L × W × H, 38.2 mm3 on the F-91W). We keep it as its own field and never print it as lug to lug.
- Lug width is listed only for watches that take a standard strap. Integrated and proprietary bands are marked as such and left out of the lug-width pages.
- Wrist fit compares lug to lug (or Casio L) with the flat top of the wrist. The flat width is estimated as wrist circumference ÷ 3.1. A ratio up to 0.75 reads compact, up to 0.89 balanced, up to 1 at the edge, and above that the lugs overhang. Both the divisor and the bands are a convention, and the tools say so.
Drawings and illustrations
Watch outlines, battery sections and movement plans are drawn by code from the numbers on the page, to scale and in millimetres. A size we lack is drawn as a dash, not invented. Bezels, dials and crowns are schematic.
Some pages carry atmospheric images of benches, tools and generic parts. They are AI-generated, made without text or logos, and never shown as a specific watch, movement or battery. Each image file carries a machine-readable AI label (IPTC “trainedAlgorithmicMedia”) instead of a caption. Pictures of a particular model are either drawings from data or freely licensed photographs with their credit.
Documents we use
646 of the 751 documents in our register are cited by at least one fact. The publishers we cite most:
- Seiko Watch Corporation 117
- Citizen Watch Co., Ltd. (MIYOTA) 90
- Casio Computer Co., Ltd. 81
- Casio America 66
- Time Module Ltd. 59
- Energizer Holdings, Inc. 39
- Citizen Watch Co. 28
- Citizen Watch US 18
- WatchSleuth 18
- Right Time International 16
- Panasonic Energy Co., Ltd. 11
- Jamtangan.com 11
- CaliberCorner 11
- eBay (third-party seller listing) 10
We take individual figures with a link back to the document, not the documents, drawings or whole tables themselves. Where a publisher’s terms restrict more, we follow them: from ETA and Sellita documents we publish single figures only, and seller catalogues whose terms forbid reuse are left out entirely. We do not copy text from manuals; we link to them.
What we do not do
- Average two sources, round a number we cannot check, or guess a missing one.
- Generate pictures of specific watches or movements.
- Identify a watch from a photo, value it, or say whether it is genuine.
- Rank products by price or take payment to change a number.
Reporting a wrong number
If a number does not match your watch or its document, tell us which page and what the source says; the way to do it is on Corrections. We check it against the document, and if the data changes, the fact gets its new source and date, and the page’s “Sources checked” date moves with it.