… of polarising material; lenses (including contact lenses), prisms, mirrors and other optical elements, of any material, …
Explanatory notes
… of polarising material; lenses (including contact lenses), prisms, mirrors and other optical elements, of any material, … finer, the successive operations being roughing, trueing, smoothing and polishing. Finally, in the case of lenses … at right angles; or (ii) a single glass plate on which small hollows, usually square, have been etched and rendered …