Notes: Reference 3525 is one of those watches that you see in the market so rarely that it's hard to really pick up an appreciation for it unless you truly seek it. The 3525 is also an historically important watch for Rolex in that it was the very first time a chronograph was placed into an Oyster case.

Oyster Chronograph, Antimagnetic, ref. 3525, Movement: cal. 13''' 23 VZ, manual, 17 jewels, signed;Dial: signed;Case: screw back and screw down “Oyster Patent” crown, 36 mm. diam.

Mechanism: Designed in 1916, the first Valjoux caliber 13, or VZ, began life as a mono-pusher chronograph utilizing a mechanism developed in 1846 by Adolph Nicole and Henri Féréol Piguet. A simple calendar complication was developed on the heels of the initial chronograph with the core design remaining in production in one of its many forms until 1974 – an astonishing 58 year run.

This is a 17-jewel, 13-ligne (about 29.5mm diameter), hacking and flyback movement of traditional column-wheel design. The 1976 technical specs for this movement can be obtained in this PDF.