21. The periods prescribed in the case of local standard capacity measures for the purposes of section 4(6) of the Act (which relates to periods of validity of certificates of fitness of local standards) shall be:
(a)ten years, in the case of a capacity measure up to and including 500 ml or 1 pint;
(b)five years, in the case of a capacity measure over 500 ml or 1 pint.