Early Chronographs (pre-Daytona) Monoblocco 3525

Rolex’s first chronographChronographA watch function for starting, stopping and resetting an elapsed-time measurement independently of the ordinary time display. in an Oyster case, with screw-down back and crown. Case, lugs and bezelBezelThe frame surrounding the crystal at the front of a watch. are one block of metal, hence “Monoblocco”; also called “Barilotto” for its barrelBarrelThe drum that contains the mainspring. shape. Two-register Valjoux 23 movement. Made in steel, yellow gold, pink gold and steel-and-gold; known serials fall in three batches.