… material; lenses (including contact lenses), prisms, mirrors and other optical elements, of any material, … unmounted, other than such elements of glass not optically worked. …
Explanatory notes
… material; lenses (including contact lenses), prisms, mirrors and other optical elements, of any material, unmounted, … of glass, optically worked, not permanently mounted . In order to distinguish between optical elements of glass of … glass. The thin film bears an impression of the lines of an original ruled grating. These gratings are used in …