The 5980/1A is the steel chronograph of the Nautilus family, introduced in 2006. It is recognisable by a single totaliser at six o'clock, in which the chronograph's minute and hour counters are read together, and by the date at three o'clock.
The 40.5 mm case has the Nautilus shape, with the pushers on the right-hand side, and sits on the integrated steel bracelet.
Inside is the self-winding calibre CH 28-520 C, an in-house movement with a column wheel and a flyback function: a single press of the pusher resets the running chronograph and starts it again immediately.
The same calibre also powers the 5968A in the Aquanaut line. The movement is visible through the sapphire caseback.
On a pre-owned 5980/1A we test the chronograph fully: start, stop, reset and flyback, and whether the counters return exactly to zero. We also assess the finishing of case and bracelet, the pushers and the crown, and compare the numbers with the certificate.
What a complete set includes is explained in our guide to box and papers.