An arm holds a pallet jewel against a ratchet wheel which is thinner than the pallet jewel, and the arm is fitted with fingers which lie on either side of, but do not touch, the ratchet wheel. In case of mechanical shock to the system in a direction transverse to the ratchet wheel, the fingers come into contact with the face of the wheel and prevent disengagement of the jewel from the wheel.
A device for indicating the maximum reading of a measuring instrument of the type having a needle turnable over a dial marked with a graduated scale extending for more than 360.degree. includes an auxiliary needle mounted on a pivot pin carried by a transparent screen covering the dial and lightly frictionally engaged with this pin so that it can be turned, for zero setting, by rotation of the pin by means of a knob attached to the outer end thereof. The auxiliary needle is provided with engagement means by which it is engaged by the main needle upon advancing movement, but which allows the main needle to pass the auxiliary needle should it require to do so, having reached a maximum position more than 360.degree. from the zero of the scale so that, upon returning to zero, it passes the auxiliary needle which remains fixed at the maximum position reached. The engagement means comprises a resilient latch including a leaf spring engaged by the main needle in its advancing movement, but resiliently deflected by the main needle as it passes the auxiliary needle in its return movement.
