Plug-socket sunk in natural stone; there's no difference in the material. Furthermore the inside of the stone can have the same finishing layer as the surface of the stone.
Robert Oberheim. Nizo 80 Movie Camera. 1968. Braun AG, Frankfurt, Germany, est. 1921. Aluminum and plastic. 4 3/4 x 10 3/8 x 2" (12.1 x 26.3 x 5.1 cm). Gift of Braun North America. 456.1970. Architecture and Design
Light switch / push-button / stone LAP(R)IS VAN DEN WEGHE