5. Nothing in these Regulations prevents the showing and use of a regulated measuring instrument which is not in conformity with the requirements of these Regulations at a trade fair, exhibition or demonstration for the marketing of regulated measuring instruments, provided that a visible sign clearly indicates—
(a)the name and date of the trade fair or exhibition;
(b)that the instrument is not in conformity with these Regulations; and
(c)that the instrument is not available for sale until brought into conformity with these Regulations.