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Rolex Extra Prima
Last updated: July 26, 2025
Brand
Caliber Number
Aegler 877 (Representative Caliber)
Production Period
1928 – 1940s
Lignes
9.75 x 14.5 Lignes
Diameter
N/A (Form Movement, 20.5mm x 32mm)
Height
5.5 mm
Power Reserve
Unconfirmed
Frequency
18,000 bph (2.5 Hz)
Jewels
15, 17, or 18
Escapement
Swiss Lever Escapement
Anti-Shock Device
None (typical for the era)
Hand Count
3 (Hours, Minutes, Small Seconds)
Manufacture Region
Unconfirmed
Functions
Hours, Minutes, Subsidiary Seconds
Rolex Extra Prima Description
“Extra Prima” is not a specific caliber, but a quality designation used by Rolex for their high-grade movements in the early 20th century, supplied by the manufacturer Aegler. A prime example is the Aegler 877, a rectangular “form” movement used in the iconic Rolex Prince. This manually wound caliber was known for its precision, often featuring a large balance wheel and a high level of finishing and adjustment. The “Extra Prima” stamp signified that the movement was regulated for chronometric performance across multiple positions and temperatures, representing the upper tier of Rolex’s offerings at the time.
