The Rolex Daytona reference 16520 debuted in 1988 and was the first Daytona to house an automatic movement. Rolex used a heavily-modified Zenith El Primero movement to power the reference 16520. This new Daytona came in a larger case with a sapphire crystal and was available in stainless steel, yellow gold, and, for the first time, two-tone yellow gold and steel. The reference 16520 became an immediate success. This particular example is from 1991 and features a beautiful white dial with partially black registers and "Daytona" in red text, reminiscent of the "Big Red" and early "Paul Newman" Daytonas. This example also feature the inverted "6" in the bottom sub-dial. The reference 16520 line was discontinued in circa 2001 when Rolex introduced their first in-house chronograph movement. Rolex Daytona's housing the El Primero movement are gaining popularity among collectors and are becoming highly sought after.