… curved, bent, hollowed or the like, not optically worked; hollow glass spheres and their segments, for the …
Explanatory notes
… curved, bent, hollowed or the like, not optically worked; hollow glass spheres and their segments, for the … hygrometers, barometers and similar appliances. In other words the heading covers a range of glasses of types … faces, and are not intended, in practice, for optical working. Nevertheless, should they be optically worked they …