The Rolex Caliber 1520 is a self-winding (automatic) mechanical movement introduced in the mid-1960s and produced through the late 1980s. It was one of the earliest movements in Rolex’s renowned 1500-series, a foundational generation of automatic calibers that elevated the brand’s standards in precision, reliability, and serviceability. While the Caliber 1520 was not chronometer-certified like its more famous sibling—the 1570—it was still built to exceptionally high standards and used widely across entry-level Rolex Oyster models.

Technical Specifications

• Type: Automatic (self-winding)

• Functions: Hours, minutes, central seconds

• Jewels: 26 (early versions had 17 or 25)

• Frequency: 19,800 vibrations per hour (vph)

• Power Reserve: Approximately 42–44 hours

• Shock Protection: KIF

• Hacking Seconds: No

• Chronometer Certified: No (typically marked “Precision”)

• Date Function: No (Cal. 1525 included the date)

Key Features and Design

The Caliber 1520 shares its base architecture with other 1500-series movements and includes:

• Bi-directional winding rotor, using Rolex’s Perpetual system

• Free-sprung Glucydur balance wheel with Microstella regulation screws

• Rugged full balance bridge for enhanced shock resistance

• Modular construction allowing for straightforward service and parts replacement

• High-grade finishing, though slightly less elaborate than chronometer models

It uses a non-hacking seconds mechanism, meaning the seconds hand continues moving when the crown is pulled out—unlike the later 1570.

Watches Powered by Caliber 1520

The Caliber 1520 was widely used in entry-level Oyster Perpetual watches, including:

• Rolex Oyster Perpetual Ref. 1002

• Ref. 5500 (Air-King) – One of the most famous uses of the 1520

• Ref. 6426 – Manual-wind, but sometimes incorrectly associated due to dial style

• Ref. 6694 (manual wind, often confused with automatic models)

These watches were typically:

• Non-date models, marked "Precision" or "Super Precision" on the dial

• Sized around 34 mm, using Oyster cases in steel or gold-cap

• Fitted with acrylic crystals, Oyster bracelets, and simple baton dials

Reliability and Servicing

The Caliber 1520 is well-known among watchmakers for:

• Outstanding durability and simplicity

• Ease of servicing, with accessible parts and straightforward assembly

• Longevity, often running well for decades with routine maintenance

It is still highly serviceable today, and its lower beat rate (19,800 vph) reduces wear on internal components, further enhancing its life span.

Collectibility and Value

While not as collectible as chronometer-certified calibers like the 1570 or 1530, the Caliber 1520 holds significant value among enthusiasts due to:

• Historical importance in the development of Rolex’s automatic line

• Role in the Air-King legacy, particularly Ref. 5500

• Mechanical purity, offering a clean, no-date Rolex experience

• More accessible pricing, making it a great entry point into vintage Rolex collecting

Collectors often seek original dials, hands, and bracelets, especially those with the correct "Precision" marking that corresponds to the non-chronometer movement.

Final Thoughts

The Rolex Caliber 1520 is a mechanically simple yet highly reliable automatic movement that played a crucial role in Rolex’s history. Though overshadowed by its chronometer-rated cousins, it powered some of the brand’s most iconic and enduring watches, especially in the Oyster Perpetual and Air-King lines. For those seeking vintage Rolex charm, dependable performance, and understated design, the 1520 remains a robust and rewarding movement to own and wear.