# ETA 6498-1 reference evidence and inventory audit

Checked 13 November 2026. This is a documented reconstruction. Its public references establish selected specifications, part identities and assembly relationships; they do not certify the reconstructed solid geometry. Inventory checks always retain `geometry: unverified`.

## Evidence precedence

| Source | Revision / date | Used for | Limits |
|---|---|---|---|
| [ETA technical communication](https://portal.eta.ch/en/technicaldocuments/index/pdf/id/1914/) | CT 6498-1 FDE 482382 **12**, 6 May 2025, 24 pages | Printed p1 specifications; p3 identities, variants and quantities; p6–17 sequence | Public service illustrations do not supply complete production geometry or tolerances. |
| [Historical ETA construction illustrations, third-party mirror](https://www.files.masteroftime.ch/6498-1%20ETA%20Technical%20communication.pdf) | CT 6498-1 FDE 482382 **10**, 31 January 2020, 24 pages | Printed p6–15 assembly and flat-part illustrations, rendered locally for silhouette/construction inspection | Historical manufacturer drawings, not measured 3D geometry. Current 2025 BOM identities and quantities take precedence. Local copy: `CT-6498-1-2020.pdf`. Per-part construction links identify the historical date. |
| [ETA manufacturing information, third-party mirror](https://www.files.masteroftime.ch/6498-1%20ETA%20Manufactring%20%20information.pdf) | IH 6498-1 FDE 482253 **11**, 12 August 2020, 12 pages | Printed p1 envelope; p7–10 external interface drawings, particularly p8 dial layout | Manufacturer-authored historical document, hosted outside ETA. Drawing-specific revisions can differ from the cover date. Local copy: `IH-6498-1-2020.pdf`. |
| [Watchmaking.io firsthand specimen report](https://www.watchmaking.io/2022/02/2-taking-measurements-6498-calibre.html) | 21 February 2022 | Counted wheel teeth/pinion leaves and measured major diameters | A used specimen, not a factory dataset. The author reports calibration and cross-checks; measurement agreement is not a tolerance guarantee for every manufactured movement. |

The current CT has precedence for reserve: **46 h minimum, 52 h typical**. The older IH p4 gives **53 h typical**; this disagreement is retained as historical metadata. The IH p1 distinguishes **37.20 mm overall** from **36.60 mm case fitting**. The current CT headline diameter is 36.60 mm; it must not overwrite the separate overall diameter. Published height is 4.50 mm, frequency 2.5 Hz and jewel count 17. The IH p8 drawing locates small seconds 10.25 mm from the movement centre. These dimensions do not establish the complete internal mechanism.

## Part coverage and assembly parents

`js/eta-reference-data.js` records all **43 positions** on printed CT p3. Each row carries its source page, stage, variant flag, quantity, parent, geometry classification and unresolved dimensions. Flags follow the spare-parts table, including position 13 without `Var` and position 14 with `Var`; some later assembly labels differ.

| Positions | Quantity allocation | Illustrated sequence, printed CT page |
|---|---|---|
| 1, 1-1, 1-2, 2–5, 900 | One plate-body root; one bottom shock assembly; two dial fasteners; one each remaining row | 6 |
| 6–11, 901 | One each; 8 and 9 are identical supplied components in separate locations | 8 |
| 12–16 | One each | 10 |
| 17–23, 903–905 | One each | 12 |
| 24–28, 28-1–28-5, 906 | One each except two pallet-bridge screws; parent 28 has no extra physical solid | 14 |
| 29 | One | 16 |
| 902 | Six: two for train bridge 16, three for barrel bridge 18, one for balance assembly 28 | 10, 12, 14 |

Position **28** is an assembled balance-bridge parent. It passes the inventory audit only when all five separately indexed children 28-1 through 28-5 pass. An optional parent scene root has no additional physical quantity. A root labelled 28 alone cannot satisfy the assembly. Position **1** is also a supplied assembly, but the reconstruction assigns its mainplate body to root 1 and separately checks its included bottom shock assembly and dial fasteners. These are explicit reconstruction allocations, not additional manufacturer part numbers.

With this allocation, the rendering inventory contains **49 separately addressable physical roots**. This is not a manufacturer-declared total of elementary pieces: supplied assemblies such as the barrel, jewelled bridges, shock settings and regulated balance contain further constituents. Do not sum assembly parents and children as independent physical parts. The single-stud note on CT p15 also prevents inferring two physical studs from the two delivery descriptions.

Screw 903 has a **left-hand thread**. The current CT p13 identifies the handedness next to the crown-wheel screw; the corresponding historical illustration was visually cross-checked. Thread pitch, profile, engagement and fastening torque remain unverified. Quantities are independent of the number of mesh subobjects used to draw a screw or jewel.

## Derived motion

The specimen counts are barrel 88; centre 80/12; third 60/10; fourth 70/8; escape 15/7; minute assembly 36/10; cannon 12; hour 40; ratchet 56; crown 35; setting wheels 16. Numerators are wheel teeth and denominators are pinion leaves.

At five beats/s and half an escape tooth released per beat, the escape period is 6 s. Reversing each external mesh produces fourth 60 s, third 450 s, centre 3,600 s and barrel 26,400 s. The cannon/minute indication shares the centre's hourly revolution. The intermediate minute wheel takes 10,800 s; the hour indication takes 43,200 s. Positive angular direction is clockwise viewed from the dial. These are prescribed kinematic relationships; the displayed geometry is not a gear-contact solution. Balance energy, real amplitude, friction, torque and timekeeping rate cannot be deduced from them.

`referenceRates(timeSeconds)` returns signed periodic radians, nominal periods and explicit kinematic/no-force metadata. `minute` denotes the minute indication; `minuteWheel` distinguishes the intermediate compound wheel. Input must be a finite number. Remainders are taken before angular conversion so even very large finite times return finite angles.

## What the automated audit proves

`auditReference(instances)` accepts actual component-root records `{id, position}` and returns all 43 source rows. It checks separately identified quantities, exposes missing/excess roots, rejects unknown or malformed positions and prevents repeated IDs from creating evidence. Assembly 28 is checked through its children. All returned rows keep identity `documented` and geometry `unverified`; there is no aggregate accuracy percentage.

The pure tests independently exercise the full position set, repeat fasteners, supplied-assembly accounting, external-mesh periods/directions, finite inputs and malformed inventories. A synthetic complete fixture passing these tests proves the audit logic, not that the current scene has passed; the application must audit its actual roots and verify selection, handling and visual construction separately.

Remaining unknowns include exact profiles and internal depths, tolerances, arbor and pivot fits, complete tooth curves and phasing, spring construction and preload, escapement working faces, bearing adjustment, variant-specific ordering identities and factory finish. Neither public illustrations nor third-party CAD resolve these automatically. All rendered solids remain reconstructed even when an envelope dimension or tooth count is documented.