I thought the main thing the new co-axial did was offer very stable positional timekeeping? I mean I've had a 1120 Omega plus a 1861 one and both of these watch would vary greatly when laid down in different dial positions, like +2 up, +8 sideways, -2 down etc.
I thought co-axial would just be +0.5 in every single position you wear it/rest it and that's what it offered.
The positional variation tolerances for all COSC rated watches made by Omega are exactly the same. Certainly an 1861 is different because it's not a chronometer movement, but for example the Cal. 1120 Swiss lever escapement movement has the following timing tolerances:
All measurement taken over 5 positions as per COSC standards:
Average daily rate: -1 to +6 s/d
Positional variation (Delta) at full wind: 12 seconds
Positional variation (Delta) at 24 hours after full wind: 15 seconds
The timing tolerances for the Cal. 2500 movement, which is the same movement with co-axial escapement and free spring balance (so a pretty close comparison) are:
All measurement taken over 5 positions as per COSC standards:
Average daily rate: -1 to +6 s/d
Positional variation (Delta) at full wind: 12 seconds
Positional variation (Delta) at 24 hours after full wind: 15 seconds
The tolerances above are also for the Cal. 3303 F. Piguet based chronograph and are the same for the 3313 co-axial version. No difference at all.
Same for the 8500 and 9300 series COSC watches - these are all the same tolerances.
When you get to the Master Chronometer specs, things do change, so the timing tolerances for those are a little different, but not consistent across the board:
All measurements are taken over 6 positions instead of just 5:
Average daily rate: 0 to +5 s/d for most calibers
Positional variation (Delta) at full wind: 12 seconds for most calibers
Positional variation (Delta) at 24 hours after full wind: 15 seconds for most calibers
So for most calibers the average rate tolerance is a little tighter, and the positional tolerances stay the same, but are checked over one additional position.
But there are a few oddballs in there also, so some calibers have average rate tolerances of 0 to +6 seconds per day instead of 0 to +5, and a couple are even at 0 to +7 seconds per day average rate, so the spread on those are no different than -1 to +6, but are just shifted a bit faster.
In addition on some calibers the Delta tolerances are not 12 seconds at full wind and 15 seconds 24 hours after full wind, but 14 and 16, and some are 16 and 16 respectively.
Cheers, Al
