still to be verified
In one line
A 17.20 mm automatic that ETA sold for forty years as a ladies' movement, and that ended up beneath dials carrying four subdials. No longer made.
First things first: you can no longer buy one new
ETA has dropped it. What circulates now is old stock or movements pulled from old watches, and that has driven prices up on the spares market. Anyone who needs a Swiss automatic this size today reaches for Sellita.
Sellita SW100 — same dimensions, from 2018, in production
For a second-hand watch this changes nothing: watchmakers who know it are still around and parts still circulate. For a new watch advertised as “Swiss automatic movement” in a small case, what is inside is almost certainly the SW100.
2671 against 2824-2: the small one is not the big one shrunk
You hear it often enough — the 2671 is a 2824-2 in miniature. ETA's own data sheets tell a more interesting story.
| ETA 2671 | ETA 2824-2 | |
|---|---|---|
| Diameter | 17.20 mm (7¾ lines) | 25.60 mm (11½ lines) |
| Height | 4.80 mm | 4.60 mm |
| Jewels | 25 | 25 |
| Frequency | 28,800 vph | 28,800 vph |
| Power reserve | 38 hours | 38 hours |
| Lift angle | 51° | 50° |
The small one is taller than the big one. Eight millimetres less across, two tenths more thick: take width away and whatever no longer fits sideways has to be stacked upwards. That is why a small mechanical watch is rarely a slim one.
And it gives the same 38 hours from a far smaller barrel, which means a thinner mainspring working harder. From the outside you see nothing. What you get is a shorter torque margin, and any dirt shows up as low amplitude much sooner.
Where it comes from
The 2671 arrived in 1971, the same year as the 2824, and belongs to a whole family nobody looks at: ETA's 7¾-line movements. The 2670 goes without a date, the 2678 adds day and date, the 2675 carries a moonphase. All of them under eighteen millimetres across.
ETA always sold it as a ladies' movement, and for forty years that is precisely what it was: the automatic inside almost any mechanical Swiss watch made for a woman. Longines renamed it the L561. Oris took it as the base for its calibre 581.
Production has stopped. Sellita launched the SW100 in 2018 to the same dimensions, and that is what anyone needing this size fits today. Looking back, the striking thing is how little was ever written about a movement an entire segment of the market rested on.
Two things almost nobody knows
- Under four subdials sits a ladies' watch movement. The Oris Artelier Complication shows day, date, a 24-hour second time zone and a moonphase across four small subdials. All of it is a module sitting on a base from this family — sources name either the 2671 or its larger 8¾-line brother, the 2688. The finished assembly measures 23.6 mm, less than many rival moonphase calibres, which is why it fitted a man's case as readily as a woman's.
- One Hamilton carried two movements, and this was one of them. The 2013 Jazzmaster Face2Face had an oval 53 × 44 mm case that flipped over on itself: a chronograph on the ETA 2094 on one side, a three-hander on the 2671 on the other. Eight hundred and eighty-eight pieces, with both skeletonised rotors on show, one per face.
Technical data
| Type | Automatic with date |
|---|---|
| Family | ETA's 7¾-line family (2670 / 2671 / 2675 / 2678) |
| Diameter | 17.20 mm (7¾ lines) |
| Height | 4.80 mm |
| Jewels | 25 (17- and 21-jewel versions existed) |
| Frequency | 28,800 vph (4 Hz) |
| Lift angle | 51° |
| Power reserve | 38 hours (ETA official data sheet) |
| Winding | Bidirectional, rotor on a ball bearing |
| Regulation | Etachron |
| Other functions | Hacking seconds, quickset date |
| Production | From 1971 · discontinued |
What a watchmaker checks before buying one
One detail sounds like nothing and isn't: the lift angle of the 2671 is 51 degrees, not the 2824-2's 50. Leave the timing machine on its default setting and the amplitude it reads is false. It is the first place anyone who has never worked on one goes wrong.
Then the usual small-calibre business. The torque margin is short: a little stale oil, or a wheel with too much play, drops the amplitude far sooner than it would on a large movement, and the rate goes ragged straight after. A 2671 that “runs fine but stops if you leave it on the bedside table” is not running fine — it is winding just enough to keep going and no more.
Then the rotor, turning here in a tiny space. Any slack in the bearing ends with it rubbing the caseback, and on a small watch you hear that before you see it.
Spares are the awkward conversation. ETA no longer makes it. Sellita's SW100 shares the dimensions, so replacing the whole movement is workable; tracking down one specific 2671 part is not always. Before committing to a small mechanical watch, ask your watchmaker what he can still get hold of.
Watches that used it
- Oris calibre 581 — the Artelier Complication movement
- Longines calibre L561
- Tissot Le Locle Automatic Lady and Carson Automatic
- Hamilton Jazzmaster Lady Auto, and one of the two faces of the 2013 Face2Face
- Alfred Dunhill MillenniuM — rectangular case, 25 × 40 mm
The big brother, the 25.60 mm one inside half the Swiss catalogue, is the calibre 2824-2.