Charles Haley, 7 Wigmore Street was made a Freeman of the Clockmakers Company in 1781 and died in 1825. He was a pioneer chronometer maker. As this is an 18,000 count train it does not beat 'half seconds'. Co-incidence between the seconds hand and the markings on the seconds dial only occurs every four seconds starting at '60'; the very unusual 'four second intermarkers' on the dial are to check that the seconds hand is correctly positioned on its arbor.
The initials M.C.S. on the dial and movement are most likely a coded form of serial numbering, the intial 'M' indicating that it was a marine chronometer. His pocket chronometers start with the intial 'P'.