Collector’s library · Verification

Where to check a number before you trust it.

A listing says the caliber is in-house. A seller says the lift angle is 52°. A service invoice says the amplitude is “healthy.” Some of that is correct, and some of it is copied from the last listing that also got it wrong. Below is where to check, by category, before a figure goes into your own record. This covers the movement, timing and case claims once you already know what model you have; for the reference number itself, see identifying a watch by its reference number. Every source below is also listed, by category, on the technical standards page.

Movement and caliber

The caliber name on a dial or a listing is usually right; whether it is in-house, outsourced, or a modified third-party base is the detail that gets rounded off. A manufacturer's own technical documentation settles it — jewel count, dimensions, and whether a movement is a base caliber or a documented variant of one.

For a Swiss ETA-family base — a 2824-2, 2892-A2 or 7750 — ETA's own site carries the factory specification. Sellita builds documented equivalents of several of those calibers, and Sellita's technical sheets cover the SW200, SW300 and SW500 families directly, including oiling charts a watchmaker would use. Miyota's automatic calibers — the 8000 and 9000 series common in field and dive watches — have their own factory pages at miyotamovement.com.

For a vintage piece, or a caliber no longer in production, the factory site is usually gone. Ranfft's movement archive is the standing reference for that case: bridge layouts, mainspring dimensions and production years for movements dating back a century. For a broad, actively maintained catalogue across both modern and vintage calibers, including community-sourced photographs of the movement itself, Caliber Corner is the largest single index.

Timing, amplitude and lift angle

A timegrapher reading means nothing without the lift angle it was taken at — the same amplitude reads differently at 44° than at 52°, and a reading with no stated lift angle cannot be checked by anyone. Watch Vault Archive's own timing log records lift angle alongside every rate, amplitude and beat error reading for exactly that reason: a number with no method attached is not a record.

Caliber Corner's lift angle reference lists the figure by caliber for most common Swiss, German and Japanese movements. For how a timegrapher actually derives amplitude and beat error from the escapement's acoustic signal — useful when a reading looks implausible — Witschi's own documentation is the source most independent watchmakers were trained on.

Two certifications get cited as if they were the same thing. They are not. COSC certifies the movement alone, tested uncased across five positions and three temperatures over fifteen days, to a published rate tolerance. METAS Master Chronometer certifies the finished, cased watch, and adds magnetic resistance to 15,000 gauss, power reserve accuracy and water resistance to the testing. A watch can be COSC-certified without being a Master Chronometer; it cannot be a Master Chronometer without first passing COSC.

Water resistance and case material

“Water resistant” and “dive watch” are different claims. General water resistance is covered by ISO 22810; a watch described as a diver's watch is expected to meet the stricter ISO 6425, which adds overpressure testing, a running-seconds indicator visible underwater, and magnetic and shock resistance the general standard does not require. Neither standard's full text is published free — ISO sells them — but ISO's Online Browsing Platform lets you search and preview the scope of each one before deciding whether the distinction matters for a particular piece.

Case material claims are usually accurate but rarely explained. Vickers hardness is the scale most manufacturers cite: standard 316L stainless steel runs around 200 HV, the more corrosion-resistant 904L a little higher, and grade 5 titanium roughly 320–380 HV depending on treatment. Surface-hardened or tegimented steels are marketed on reaching four to six times that, and the honest way to read the claim is as a scratch-resistance figure, not a toughness one — a harder surface resists marking and is also more brittle under a sharp impact.