Eterna Caliber 520u

Eterna Caliber 520U

Eterna Caliber 520u

Brand Eterna
Caliber Number 520U
Base Caliber
Eterna 520
Movement Type Manual wind, mechanical
Diameter 12”’ (26.5mm)
Thickness 4mm
Jewels 15
Lift Angle 42 degrees (needs confirmed)
Power Reserve 42 hours
Vibrations Per Hour 18,000 bph
Balance Staff U620
Hairspring Flat
Hands 1.38mm / 0.80mm / 0.13mm
Anti-Shock Eterna-U Device
Features Hours, minutes, small seconds
Country of Manufacture Switzerland
Production Years 1940s – 1950s
Known Models 1952 Eterna dress watch

The Eterna caliber 520U is a vintage mechanical movement based on the Eterna caliber 520. These calibers were produced in the 1940s and 1950s.


The 520U movement seen here is equipped with an in-house anti-shock device called Eterna-U.

Other Variations

There are a few variations of the 520 movement with a letter designation based on the type of anti-shock device used. The ones we know about are:

  • 520 – the base caliber (4mm height)
  • 520H – Eterna-H shock absorber
  • 520L – Eterna-L shock absorber
  • 520S – central sweeping seconds (4.95mm height)
  • 500U – shown here

If you know more about these variations of the caliber 520, or know of some not listed, please leave the information in the comments.

The movement pictured above was found in a vintage Eterna dress watch here.

About Eterna

Eterna was founded in 1856 in Grenchen, a municipality of Solothurn, Switzerland. Despite many people thinking that Eterna is part of the Swatch Group, the watch brand is owned by a Hong Kong watch conglomerate known as Citychamp Watch & Jewelry Group. ETA, the movement branch of Eterna that was established in 1932, became part of the Swatch Group and still produce movements that we know today. Eterna also still produces movements and modules for modern timepieces.

Please share your experiences and thoughts about the Eterna caliber 520U in the comments section below…

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4 years ago

[…] movement is the Eterna 520U with 15 jewels and a hidden ratchet wheel and crown wheel. It’s Eterna’s first caliber […]

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[…] presumably the most versatile watch that I own. A 1952 Eterna ref. 106BDT, with Eterna’s in-house calibre 520U inside. It’s understated, but neither not enough nor too much. Just a simple watch in excellent […]

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