ETA Caliber 251.233 COSC

The ETA caliber 251.233 is a thermocompensated quartz chronograph watch movement. This caliber is Swiss made with 27 jewels. Official documentation has been found dated February 18, 2008, so this movement has been available since at least that long. 251.233 was introduced as a direct replacement for the ETA caliber 251.232. This is a repairable quartz movement – if yours is having issues, it could be a bad coil.

Unique Chronograph Functionality:

Rather than having a subdial for the 60 minutes totalizer, the 251233 has a central 60 minutes counter hand behind the central chronograph seconds hand. Other complications include a 1/10 second counter at 2:00, a 12 hour chrono counter at 10:00, a running small seconds indicator at 6:00, and a date calendar at 4:00.

Discontinued:

This movement appears to be discontinued. It is not found on the ETA website, nor can replacements be easily found online. Please comment below and share everything you know about this movement.

Caliber Commentary:

From Invicta:

“In this circumstance, the Thermo Compensated Movement is being utilized in these watches. The thermo compensated movement is made by ETA 251.233 and is comprised of 27 jewels. This fact differs from most quartz movements which generally do not have any jewels in the movement. The ETA 251.233 in entirely Swiss Made. These are the most accurate certified quartz caliber movements currently available; the movement maintains a -15 seconds per year. Due to their exceptional accuracy, thermo compensated quartz watches take accuracy in performance to another level in timekeeping.” (Source: http://www.invictawatch.com.hk/invicta/images/events/Store.pdf)

From Christopher Ward:

“To gain chronometer status, watchmakers submit their Swiss movements to COSC, an independent, non-profit making watch accuracy verification organisation based in Geneva, to be tested against the international standards of ISO and DIN.

Certification follows exhaustive testing. In achieving the coveted status of Certified Chronometer, a movement must not only be made from the highest quality components, but also be the object of special care on part of the finest horologists and technicians as it is painstakingly assembled.

Only movements which meet the precision criteria are granted an official certificate. Each uncased movement is individually tested for fifteen days, in five positions, at three different temperatures.

Movements are fitted with a second hand for tests and measurements are made daily with the aid of cameras. Based on all of these measurements, seven eliminatory criteria are calculated, each of which must be met.

The exacting and rigorous nature of the COSC certification process means that the achievement of Certified Chronometer status is extremely rare. In fact, of all the watches produced in Switzerland each year, just 3% bear the coveted COSC ‘bulletinde marche’ or certificate of watch performance.Which is why, when you read the words ’Certified Chronometer’ on a Swiss watch you can be sure that the movement behind the elegant dial is a rare example of fine Swiss watchmaking which is accurate, precise… and extremely rare.” (Source: https://www.christopherward.com/media/manuals/c7cosc_manual.pdf)

Battery Cell Strap Macro:

ETA 257.233 Tech Docs (PDF):

Additional Resources:

• Official instruction manual from Christopher Ward
• COSC VS Chronometer