in the "V" of "VII" to be specific. Two examples include the Astrotourbillon and Tortue perpetual calendar.


But a change in position to "X" is sometimes necessary due to the dial design or complication.
So for instance in the Calibre de Cartier it is at "X" because there is no "VII".

While in the Santos Triple 100 it is deemed to look better in "X" than "VII".

While in the Tank made for the handover of Hong Kong there is a "7" so it is at "X".

- SJX
So for instance on the Santos Triple 100 it is at "X" because it looks better there than at "VII".

The position of the secret signature is not an indication of production date.
Thanks for the great question.
- SJX