The Jules Audemars Chronometer from AP which came out a few years ago features an interesting movement (cal. 2908) with some resemblance to the Omega co-axial. Here are some characteristics: - Unlike to the typical Swiss Lever escapement, the locking function and the impulse function are done by separate jewels in the 2908. This is more akin to the Co-axial escapement or a marine chronometer's Spring Detent Escapement. The Swiss Lever escapement design is a very good compromise between accuracy and reliability but has the disadvantage of escapement wheel teeth sliding on jewel surfaces which in turns necessitates lubrication for proper operation and reliability. The lubrication's characteristics changes over time, compromising timekeeping accuracy. In addition, the Swiss Lever escapement has some loss of power in operation. AP novel escapement configuration sidesteps these disadvantages by separating the locking and impulse functions and having little slide. - No lubrication of the escapement jewels. This feature improves -at least in theory- the long term time keeping accuracy of the watch compared to a conventional watch. This was George Daniels' motivation for the creation of his escapement design but Omega uses lubrication on its implementation. - High beat operation: 43 200 beats per hour, instead of the usual 18 000, 28 800, etc. High beat operation reduces the time for a watch to react to a change of position of the watch. - The 2908 uses two hairsprings, operating co-axially on the balance wheel axis, but wound in opposite directions. This is said to improve isochronocity. I see two effects of adding a second hairspring on the performance of the watch. 1) It would reduce positional variances because hairsprings are inherently physically asymetrical and by having a pair cancels out some the effects caused by this asymmetry on timekeeping performance. 2) my guess is that the escapement configuration of the 2908 reduces escapement error and the movement designers found themselves with a movement with worse isochronicity when using a single typical flat hairspring. Indeed a modern Swiss Lever escapement has some escapement error but it is compensated by the hairspring design. The typical flat hairspring with no overcoil "develops" asymmetrically and causes it to run anisochronaly, but this can be used to compensate anichronicity caused by escapement error. This is speculation on my part of course but I'm curious to know the design reasons to add a second hairspring.