When a bottom plate and a watch dial are made of different materials, they are subject to differential expansion, because of the different expansion coefficients of their materials. Consequently, a dial secured to a bottom plate, and of generally much smaller thickness than that of the bottom plate, may bow or retract with variations in temperature. In some critical cases, particularly at high temperatures, for example in tropical or desert areas, this type of deformation may cause the hands to come out, which makes the watch unsuitable for use.
CH Patent Application No 120 846 A, in the name of BOVET FRERES, discloses the securing of a dial onto a bottom plate using clips cooperating with pins. U.S. Patent Application No. 543 628A, in the name of MARSH, discloses a similar device.
CH Patent Application No. 82 809 A, in the name of WILLIAMSON, discloses a device for securing a dial with feet by clamping the dial feet, housed in a cavity of a slot in a stamped bottom plate, by angularly folding radial fingers comprised in said bottom plate.
CH Patent Application No. 125 760, in the name of GAERTNER, discloses the securing of a dial with feet by elastic retention of the feet using spring flanges held by screws.