A late 20th century silver 'Prisma' mystery desk timepiece

A late 20th century silver 'Prisma' mystery desk timepiece
signed Cartier, numbered 215362, the silver case with Swiss hallmarks
Rectangular reeded silver case fitted with a signed silvered Roman dial viewed via a prism, the image of the dial appearing and disappearing depending from where it is viewed, the Imhof quartz movement with hand setting knop to the underside, height 9.5cm.