Eterna 520S: A Vintage Caliber Gem for Enthusiasts
The Eterna 520S stands as a pioneering manual-wind movement from Eterna, marking the brand’s first caliber tailored for men’s wristwatches in the early 20th century. Prized by vintage collectors and hobbyist watchmakers, its robust construction and elegant finishing embody Swiss precision from the interwar era, often found in tonneau-shaped cases with custom bridges for brands like Stauffer.
Historical Context
Introduced around the 1920s-1930s, the 520S evolved from Eterna’s early designs, featuring interchangeable bridges for aesthetic customization while retaining core components. Its “fingerprint” elements, like the setting lever cover plate and spring detent, ensure easy identification amid variations. Collectors value it for reliability in period pieces, with late samples blending old and new mounting threads for versatility.
Technical Specifications
Size: Approximately 8¾ lignes (20mm width), ideal for tonneau cases.
Jewels: Typically 15-17 jewels.
Beat Rate: 18,000 vph (5 Hz).
Power Reserve: Around 40-45 hours via Eterniflex mainspring (Zf968, 1.35 x 10.5 x .10mm).
Balance: Glucydur screwed balance with Nivarox hairspring; Eterna-U shock protection.
Keyless Work: Stem W620; concealed winding elements in some variants.
Balance Staff: U620 for precise pivoting.
Functions: Hours, minutes; sub-seconds at 6 o’clock.
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Watch Parts Enquiry
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Stem, Crown, Hands & Spares might be available for this movement.
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