Integrating two mechanical movements within a single case is however costly and requires a considerable thickness.
Watches comprising a single mechanical movement capable of displaying indications on both opposite faces are also known; such movements, which are complex and often produced in limited quantities, are also expensive.
Watches comprising two
quartz movements head-to-
tail are also known, but they have neither the advantages nor the prestige of mechanical movements.
The turning-over mechanism in this case takes up the space around the case usually allotted to the time-set button and other control elements, which implies strict aesthetic constraints for the watch designers and manufacturers.
Such a pivot must thus be machined with a very high precision, which makes the mechanism more expensive.
Turning over the watch requires moving the case relative to the frame along a complex three-dimensional trajectory that is difficult to determine, and generally requires the user to hold the glass or glasses between his fingers, leaving finger prints.
Furthermore, the reliability of the turning-over mechanism is problematic since the pivot can jam / shrink or even break under the effect of even small impacts or torsions.
Finally, the case and in particular the protruding elements of the case, such as control buttons, run the risk of coming into contact with the external frame during pivoting, which may scratch and mark them.
In this case also the case is connected to the external frame through a single pivot, which causes reliability problems and
machining difficulties.
In particular, it is impossible to place control buttons or winding buttons that are too protruding on the lateral side of the case close to the turning-over axis, as these elements would then risk colliding with the frame's bottom during turning-over.
This solution is thus not adapted to watches having control elements on two opposed lateral sides, notably watches comprising simultaneously protruding control elements on a first portion of the periphery of the case between 12 o'
clock and 6 o'clock and protruding control elements on a second portion of the periphery of the case between 6 o'clock and 12 o'clock.
The case and the winding button at this occasion risk coming into contact with the frame 21, which could scratch or even damage them.
Finally, in most of the described solutions, a large portion of the slides are apparent at least during certain turning-over steps, which is not very aesthetic and especially risks them being exposed to dust or
skin particles that can in certain cases block them and prevent the watch from turning over.
Finally, the slides are wearing parts that cannot, or only with difficulty, be replaced when inaccuracies arise in guiding the case.