Use this guide in three steps
- Write down the required displays and functions. Distinguish ordinary seconds from elapsed-time counters, and date from day-date.
- Identify the actual movement. Record its claimed maker and full reference, including suffixes, separately from the watch's model name.
- Follow the relevant reading route. Use the table below to reach the page that resolves your particular question.
| What you need to understand | ETA reference example | Useful next step |
|---|---|---|
| Automatic time and date | 2824-2 or the slimmer 2892A2 | Compare the full reference and package dimensions. Read the 2892 family history if different suffixes or reserve figures appear. |
| Automatic day and date | 2836-2 | Separate the two calendar displays and obtain the instructions for the fitted movement. |
| Working elapsed-time counters | 7750 | Use the 7750 chronograph observation table to record which counters work. |
| Manual winding and small seconds | 6497-1 | Confirm manual operation and the large movement package; do not expect an automatic rotor. |
| An ETA versus Sea-Gull comparison | 2892A2 versus TY2661/ST1812 | Use the specific specification and fit comparison, rather than applying all ST18 labels to one reference. |
The 6497-1 is included as a manual-wind contrast to the automatic references. It explains why winding method and small-seconds layout matter; this guide does not establish it as a replacement for a Rolex-style movement.
A compact manufacturer reference
These are ETA's current listed packages and typical reserves, checked on 14 October 2026. “Typical” is a published reference value. Older documents, altered mechanisms and individual watches require their own assessment.
| Reference | Winding and display | Diameter × height | Listed typical reserve |
|---|---|---|---|
| 2824-2 | Automatic; central time and date | 25.60 × 4.60 mm | 42 hours |
| 2836-2 | Automatic; central time, day and date | 25.60 × 5.05 mm | 42 hours |
| 2892A2 | Automatic; central time and date | 25.60 × 3.60 mm | 50 hours |
| 7750 | Automatic; small seconds, day-date and chronograph | 30.00 × 7.90 mm | 54 hours |
| 6497-1 | Manual; hours, minutes and small seconds | 36.60 × 4.50 mm | 52 hours |
For time-and-date descriptions, the visible practical difference between the 2824-2 and 2892A2 listings is their movement height. The 2836-2 adds the weekday display and additional height. Those facts help interpret the design brief, but a case, dial and movement holder must still be matched to the actual reference.
BPH, VPH and hertz
Beats per hour (BPH) and vibrations per hour (VPH) normally count half-oscillations of the balance in mechanical-movement descriptions. Hertz (Hz) counts complete oscillations per second. Divide VPH by 3,600 to obtain vibrations per second, and divide that result by two to obtain Hz.
- 28,800 VPH ÷ 3,600 = 8 vibrations per second = 4 Hz.
- 18,000 VPH ÷ 3,600 = 5 vibrations per second = 2.5 Hz.
ETA lists 28,800 VPH for the four automatic references above, and 18,000 VPH for the 6497-1. The latter is not “2.5 ticks per second”: 2.5 is its full-oscillation frequency. A frequency figure describes the oscillator, not a measured daily-rate result or a manufacturer's identity.
Manufacturer, style and modification are different entries
| Wording in a listing | What needs to be resolved |
|---|---|
| “ETA 2824-2” or another complete ETA reference | A claim about maker and reference; verify the installed unit before assigning the manufacturer's record. |
| “ETA-style” or “Asian 7750” | A supplier description with incomplete identity. Obtain the actual maker, version and functions. |
| A decorated or modified calibre | Identify both the mechanism and what was added, removed or relocated. |
One crown position or a familiar counter layout can be an observation, but is not a complete movement identification. The identification section connects labels with the evidence to retain. The function checks cover calendars and GMT mechanisms outside this ETA reference list.