… Lenses, prisms, mirrors and other optical elements, of any material, mounted, being parts of or fittings for instruments or apparatus, other than such elements of glass not optically worked. …
Explanatory notes
… 90.02 ‑ Lenses, prisms, mirrors and other optical elements, of any material, mounted, being parts of or … does not include mounted optical elements which are in themselves separate appliances, for example, hand magnifying … for astronomical instruments, binoculars or refracting telescopes, microscopes, etc. (4) Mounted prisms for …