The Cal. 2403 comes in an A and a B version. The A is a 28,000 A/h beat rate, and the B is the slower 25,200. Power reserve is 44 for the A, and 48 for the B.
So if you are familiar with the 2500 variants, the 2403A is like the 2500B version, and the 2403B is like the 2500C.
The 2403, like all the 2 level co-axial escapement designs, suffers from the build up of sticky residue on the intermediate escape wheel due to the shape of the teeth. The B version has an upgraded intermediate escape wheel available that helps to resolve this problem.
Hope this helps.
Cheers, Al
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