Scientific, surveying, optical, weighing, measuring, signalling, checking, supervision and recording instruments and apparatus, in particular equipment, apparatus and instruments for flow measuring, level measuring, volume measuring, temperature measuring, mass density measuring and/or pressure measuring, current/pneumatic transformers and valve setting regulators; parts and fittings for all aforesaid goods; gas mixers; apparatus and instruments for conducting, switching, transforming, accumulating, regulating or controlling electricity