On September 5th, 2007 Omega filed a patent for a rather specific case construction. It is our believe that this technique would later be used in the Omega Speedmaster Dark Side of the Moon 3188.8.131.52.01.003
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A few notable excerpts that explain the background behind this patent;
Timepieces whose case includes a middle part made of a hard, natural or synthetic mineral such as sapphire, ceramics or a natural or reconstituted jewel, are already known. Such materials do not withstand mechanical stress very well and efforts have therefore been made to reduce machining operations as far as possible or to limit them to machining a housing for a timepiece movement and through passages for the control member stems.
It is thus an object of the present invention to overcome the drawbacks of the aforecited prior art by providing a case that has an outer middle part made of natural or synthetic mineral material, such as ceramics, which is assembled without being subjected to mechanical stress.
The invention therefore concerns a watch case with a composite middle part formed by two essential parts, one forming the outer middle part made of a mineral material, and the other forming the inner middle part made of a metal that can easily be machined to enable all the other watch components to be assembled. The invention is characterized in that the inner middle part is itself made in two parts, formed by two rings, designed and mechanically assembled to each other so that they can lock the outer middle part with a slight play.