If you have bothered to search and read the posts I've written about this in the past (both here and at WUS Omega forum) you will know what the issue is with the C and previous revisions.
By the way the D was not superseded - it is still a current movement in the Omega line up. It, and all other currently produced Omega co-axial movements, have the 3 level escapement that resolves the issues of the early 2500 and other 2 level escapement movements.
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