Stroboscopes; Tachometers; Electronic spectrophotometer for use in identifying and measuring colors; Electronic ultrasonic test equipment, namely, ultrasonic flaw detectors, thickness testers and hardness testers, for non-medical use; Metal hardness testing machines; Optical sensors; Scientific apparatus, namely, spectrometers and parts and fittings therefor; Surface roughness testing machines and instruments; Surveying instruments; Testing apparatus for testing printed circuit boards