thanks for the measurement. As WastedYears posted...the Chronoscope clasp is 15mm like the 3861 bracelet and probably Fratello guessed or got that number from Omega...
I think the pic below from post # 18 (Chronoscope clasp on the bottom and installed, 3861 clasp on the top) shows how Omega is able to not show the endlink when the Chronoscope clasp is fully extended when looking at it from a top view and is able to achieve a flush width look as the bracelet.