Abstract: The polygonal flat glass 1a stretches itself out to the edge of the watchcase except on two diametrically opposed sides, where it is held between portions 3 by cylindrical pins 6 clamped within through holes formed by two semicylindrical grooves 7, 8 provided in the metallic case section and in the glass, respectively. The glass 1a and the pins 6 are held transversely in place by the pressure which gaskets 10, 11 exert on the glass. Rough walls of grooves 7, 8 and pins softer than the metallic case section and the glass increase the clamping action of gaskets 10, 11. An opaque mask formed under a peripheral glass area hides gasket 11 and the upper face of the spacing ring 14. The glass sides secured to the middle case section 2a could also be curvilinear.