Section 18 OPTICAL, PHOTOGRAPHIC, CINEMATOGRAPHIC, MEASURING, CHECKING, PRECISION , MEDICAL OR SURGICAL INSTRUMENTS AND APPARATUS; CLOCKS AND WATCHES; M USICAL INSTRUMENTS; PARTS AND ACCESSORIES THEREOF 90 Optical, photographic, cinematographic measuring, checking, precision, medical o 90 23 Instruments, apparatus and models, designed for demonstrational purposes (for ex 90 23 00 90 23 00 00 Commodity Code Description 90 23 00 00 00 Instruments, apparatus and models, designed for demonstrational purposes (for example, i