In 1987, Rolex made a major upgrade to their Daytona line of chronographs: an automatic movement, based on a Zenith El Primero ébauche.
The present chronograph is a very early representative of that historical model, reference 16520, as denoted by its L serial number. Offered in glorious condition and with its original Guarantee, this specimen is particularly interesting as it is one of the very few L series sporting what can be considered the nearly definitive layout for the reference. In fact, in the first few years of commercialization of this model, Rolex modified the graphics of the dial (5 lines staccato, then 4 lines, and finally 5 lines) and of the bezel (2 different versions graduated to 200 UPH, and finally to 400 UPH). Only very few, the latest produced, L series feature the final layout with bezel graduated to 400 units, and 5 lines dial. The one detail of this dial which will be later modified is the upside-down 6 in the 12 hours register, which will be rightside-up from 1993.
Consigned by its original owner the present Cosmograph Daytona is furthermore preserved in very good overall condition, still retaining the protective green sticker to the case back.