OMEGA Speedmaster Chronoscope 329.30.43.51.03.001: specs and checks

A gap in the sheet, left as a gap

OMEGA's page for this reference publishes the diameter, the lug-to-lug span, the distance between the lugs, the weight, the crystal, the rating, the calibre, the movement type and the reserve.

It does not publish a case thickness.

That is worth stating plainly rather than quietly filling in, because filling it in is exactly what happens on most listings. Another Speedmaster's figure gets borrowed, or a number from a forum gets repeated, and a specification appears that the manufacturer never stated.

The honest handling is in two parts. Say that OMEGA does not publish it. Then, if the buyer needs the figure, measure the watch in front of you with callipers and give them your measurement, described as yours.

That distinction — what the maker states versus what you observed — is the whole basis of a reference page that can be trusted, and this reference is a good example of why it matters.

Manual winding, with the usual warning

The calibre 9908 is manual-winding, with 60 hours of reserve and Master Chronometer certification.

Several Speedmaster references in the same collection are self-winding, so confirm which you are holding. The tell is immediate: turn the crown and feel whether it does anything.

Then the caution that applies to every hand-wound watch and gets forgotten on the ones that look like sports chronographs. When the crown stops, it has stopped. A manual mainspring has no slipping mechanism protecting it, and an owner accustomed to automatics who keeps turning will break it.

Say so at handover. Check on inspection whether somebody already did.

Run the chronograph, do not just click it

Most chronograph inspections consist of start, stop, reset. That proves the pushers work and very little else.

A running chronograph draws on the movement. A watch whose amplitude has fallen away will keep good enough time on its own and then lose noticeably once the chronograph is engaged — which is precisely the fault a three-second test cannot find.

So start it and leave it running for a few hours while you do other things, then compare against a reference. Reset afterwards and confirm every hand returns exactly to zero; a seconds hand that stops a hair short of the mark is the commonest chronograph fault there is.

The numbers that describe it on a wrist

43 mm across, 48.60 mm lug to lug, 21 mm between the lugs, 145 g complete.

The lug-to-lug is the figure to lead with. Forty-eight and a half millimetres is a substantial span, and it — not the diameter — determines whether the case sits flat.

Twenty-one millimetres between the lugs is the awkward part for anyone planning a strap change: it is between the two sizes that are widely stocked, so mention it before they go looking.

Water resistance is 5 bar (50 metres / 165 feet). The crystal is sapphire treated on both faces, so grade the outer coating as well as looking through the glass. Dial listed as blue, case as steel, clasp a foldover with comfort setting whose micro-adjustment should click into each position and hold.