I thought this a little odd until I realized that the centre part of the dial is a separate part and can, in fact, be rotated by applying a gentle torque. I guess that, when new, the centre dial was correctly aligned and it has moved over the last 250 years!
I notice that the centre part on the beautifully preserved Watch No. 8346 appears also to be very slightly misaligned (although this could be distortion in the photograph). The centre part also includes the word LONDON which mine does not.
I must do a little research to see if I can discover identical "Champlève" outer dials on watches signed other than Kover.
Readers' comments would be appreciated - maybe there's an obvious and completely different reason that I've missed.