ROLEX, DAYTONA REF. 16520 'ZENITH', A STEEL AUTOMATIC CHRONOGRAPH WRISTWATCH

The first automatic versions of the celebrated Daytona reference featured movements made by Zenith. The Cal. 4030 movement was based on the El Primero movement, but was modified (from a 5 Hz high-beat calibres to 4 Hz versions) by Rolex. From 1988 to 2000, Rolex used these Cal. 4030 movements till they developed their first in-house movement, the Cal. 4130.

The Rolex Daytona dials were labeled "SWISS MADE" rather than "T SWISS T" from 1999 until the end of production in 2000 due to the change of luminous material used from tritium to LumiNova.