(1) Ownership and use of the instrument or device is limited to federal, state or local government agencies in the performance of official functions.
(2) The instrument or device is of a readily portable type, not intended for use within the state in excess of 30 days annually, and for which proof exists of satisfactory examination within the immediately preceding six months by a state or local weights and measures authority. [1973 c.293 §31; 1989 c.405 §5]