Surveying machines and instruments; detectors, namely, mass spectrometers for detecting ions and parts and fittings therefor, particle detectors, gas detectors for detecting the conformation of gas, liquid detectors; measuring devices, electric, namely, mass spectrometers and parts and fittings therefor; air analysis apparatus; meteorological instruments; gas testing instruments; mass spectrometers for testing composition and quality of industrial materials; food analysis apparatus, namely, m...