ETA Caliber A31.L11

The ETA caliber A31.L11 is based on the ETA 2892-A2 automatic watch movement.

A31.L11 VS 2892-A1:

When comparing the caliber A31.L11 to the 2893-A2, one of the advantages and main differences is the improved power reserve. The 2892-A2 has a power reserve of 42 hours, while the A31.L11 can run up to about 72 hours on a full wind. ETA attributes this improvement to an upgraded alloy being used for the mainspring, allowing for the material to be thinner, and as a result offering increased flexibility and efficiency thanks to having more coils to store more energy. The barrel arbor was also reduced in size to accommodate a longer spring – hence even more coils. Are you more of a visual learner? Watch this video.

Another notable upgrade is the use of Nivachron or Silicium balance springs to reduce the negative impact that magnetism has on accuracy and functionality. Nivachron is a titanium-based metal alloy with magnetic resistant properties (video), while Silicium is made from silicon and is anti-magnetic. Not all A31.L11 movements are equipped with Silicium, so you will want to check will want to check the configuration of your particular movement to be sure.

Although the A31 family of movements is an evolution of technology (more power reserve and silicon hairsprings for example), it also appears to be a way for ETA to narrow down their offerings to Swatch Group watch brands only. Since the older movements were sold to non-Swatch Group brands for decades, there is a lot more technical data and historical information available. The new series of movements being produced by ETA are not as well known, nor as well supplied when it comes to parts. This is why the community ought to start regarding ETA as a Swatch Group exclusive movement house.

Accuracy:

Accuracy of the ETA caliber 2892-A2 can range from as much as +/-20 seconds per day to just +/-5 seconds/day. The accuracy that your watch experiences depends on the grade that the watch manufacturer chose to power their watches.

A31.L11 as a base movement:

Other brands (Swatch Group brands such as Tissot, Longines, Rado, Hamilton, Mido, Certina) may be using the A31.L11 as a base movement with their own branding and unique caliber numbers. For example, Longines uses the A31.L11 as the base for their L888 and L888.4 calibers. If you know of other watch brands using the A31.L11 as their base movement (and the corresponding caliber number), please add it in the comments below.

You might be asking yourself, why would all the Swatch Group brands designate their own caliber numbers to the same movements? There are likely a few reasons, starting with marketing of course – having a distinct caliber number reinforces a consumer’s perception of the brand and watch they are about to buy. Some hardcore watch enthusiasts might debate this, but any modification, including simply adding different finishing or branding to the rotor, is justification enough to use a different caliber number than the base. Another reason could be for organization and inventory purposes. Designating different caliber numbers between brands help them track intercompany movement/parts orders and supply better.

Additional Resources:

• ETA caliber 2892-A2
• Check back for tech sheets and pdf docs