Breitling Chronomat B01 42 AB0158101A1A1: specs and what to check

A chronograph built like a diver

Line this reference up against the other Breitling chronographs documented here and one figure stands out.

20 bars — 200 metres — with a screw-locked crown. The Navitimer chronograph on the same calibre is rated at 3 bars with a crown that does not screw down at all; the Premier at 10 bars, also without a screw-down crown.

Chronograph cases are hard to seal because every pusher is a hole through the case with a gasket in it. Getting to 200 metres with two of them plus a screw-down crown is the point of this case design, and it is a fair thing to tell a buyer who is choosing between the three.

What it does not mean is that a used example is still watertight. Three penetrations means three gaskets ageing quietly. If it matters to the buyer, pressure test it.

The bezel invites use, so test it

The bezel is unidirectional, ratcheted — dive-watch behaviour on a chronograph.

That combination has a practical consequence: the buyer will actually use it, because it does something the chronograph does not. A bezel tracks elapsed time with no pushers to remember and no reset to worry about.

Grip it and try clockwise first: nothing should happen. Then anticlockwise through a complete turn, counting the clicks and feeling for any that are soft. Set it against the minute hand, let go, and knock the watch gently against your palm — it should not have moved.

Twenty millimetres, all the way to the clasp

The bracelet is specified as 20/20 mm, and the case's in-between-lug measurement as 20.05 mm.

Most steel bracelets narrow toward the clasp. This one does not: it is twenty millimetres at the lugs and twenty millimetres where it closes.

That matters when a buyer asks about swapping to a strap. Almost every aftermarket strap is made to taper, so a 20 mm strap will fit the case and look noticeably different at the buckle. Worth mentioning rather than letting them discover it.

While you have the bracelet in hand, hold it horizontally from one end and watch how far it droops. Steel links wear at the pins, and a stretched bracelet on a watch like this is a visible and expensive fault.

The rest of the inspection

The Breitling 01 here is specified with 47 jewels, 28,800 v.p.h and approximately 70 hours, driving a chronograph that reads quarter seconds, 30 minutes and 12 hours.

Run it for the full twelve. The hour totaliser is the register nobody bothers to test and the one that reveals a movement running out of amplitude under load.

Then work the pushers separately. Start, stop, reset — each should take a similar, definite pressure and return cleanly. A pusher that feels mushy, sticky or gritty is telling you about its gasket as much as about its spring, and on a 200-metre case the gaskets are the rating.

The case back is screwed in with a sapphire crystal, so the movement is on view: check for oil around the jewels and for any mark on the rotor's path.

Case: 42 mm across, 13.77 mm thick, crystal specified simply as sapphire on this reference, without the glareproofing line the other Breitlings here carry.