26 OPTICAL INSTRUMENTS-NAMELY, PRISM BINOCULARS AND MONOCULARS, FIELD GLASSES, SIGHTING TELESCOPES, MICROSCOPES, SURVEYING INSTRUMENTS, TELESCOPES, MAGNIFIERS; PHOTOGRAPHIC LENSES; TELESCOPE LENSES; OPTICAL PRISMS; FINE MEASURING INSTRUMENTS-NAMELY, GAUGES, GAUGE-BLOCK INTERFEROMETERS, HARDNESS TESTERS, EXTENSOMETERS