The Rolex Caliber 1555 is a self-winding mechanical movement from the celebrated 1500-series, developed and used by Rolex during the 1960s and early 1970s. Closely related to the 1530, 1560, and 1575, the 1555 was specifically engineered to power Rolex’s flagship luxury watch—the Day-Date, also known as the “President.”

It combined high-end finishing, robust performance, and calendar complications that helped cement the Day-Date's reputation as a symbol of prestige and mechanical sophistication.

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Technical Specifications

• Type: Automatic (self-winding)

• Functions: Hours, minutes, central seconds, day, date

• Jewels: 26

• Frequency: 18,000 vibrations per hour (vph)

• Power Reserve: Approximately 42 hours

• Chronometer Certified: Yes (COSC-certified)

• Hacking Seconds: No

• Quickset Date/Day: No

The 1555 offered both day and date complications, visible in the traditional 3 o’clock and 12 o’clock positions on the dial of the Day-Date. Unlike later versions, the day and date had to be changed by rotating the hands past midnight, which made setting the watch more time-consuming.

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Movement Design and Features

The Caliber 1555 was built for precision and longevity, using Rolex’s proven automatic system with bidirectional rotor winding. Other notable features include:

• Free-sprung balance wheel with Microstella screws for fine regulation

• KIF shock protection on the balance staff

• Day and date calendar geartrain with slow overnight changeover

• Solid full balance bridge for stability and shock resistance

The movement was carefully adjusted in multiple positions to meet the strict standards of chronometer accuracy, even with the added complexity of the dual calendar display.

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Watches Powered by Caliber 1555

The Caliber 1555 was used almost exclusively in Rolex Day-Date models from the early-to-mid 1960s, especially:

• Ref. 1803 – The most iconic Day-Date reference, available in yellow, white, or rose gold

• Ref. 1804 – Diamond bezel variants

• Ref. 1806/1807 – Special textured cases (Florentine or bark finishes)

These models were all produced in precious metals only (no steel or two-tone), reinforcing the Day-Date’s image as Rolex’s elite offering.

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Serviceability and Evolution

The Caliber 1555 is highly serviceable, built on the same durable platform as other 1500-series movements. However, it lacks some modern conveniences:

• No hacking seconds – Second hand continues running when setting time

• No quickset – Day and date must be advanced by manually rotating the crown

Despite these limitations, the movement is extremely robust. Rolex eventually replaced the 1555 with the Caliber 1556 in the late 1960s, which maintained the same architecture but added hacking seconds for easier time setting.

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Collectibility and Legacy

Collectors admire the Caliber 1555 for several reasons:

• It represents the first generation of Day-Date movements with both day and date functions

• It powers some of the most iconic vintage Rolex references ever made

• Watches using the 1555 often feature original pie-pan dials, early President bracelets, and vintage tritium lume

While less advanced than its successors, the 1555’s historical importance, combined with Rolex’s build quality, ensures it remains a sought-after movement in the vintage Rolex world.

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Final Thoughts

The Rolex Caliber 1555 is a milestone in the brand’s mechanical development, marking the era when Rolex firmly established itself at the top of the luxury watch industry. It powered the early Day-Date models worn by presidents, CEOs, and world leaders—earning the nickname “The President’s Watch.” While it lacks some modern features, the 1555’s precision, durability, and iconic status make it a movement of enduring value and prestige.

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