12. Any drum, storage tank or other container or any delivery pump or pipe must bear an indelible notice to the effect that—
(a)where it contains, or is an outlet for, any gas oil or kerosene marked under regulation 4 (marking required for rebate), such oil is not to be used as road fuel;
(b)where it contains, or is an outlet for, any light oil marked under regulation 4 (marking required for rebate), such oil is to be used only as furnace fuel;
(c)where it contains, or is an outlet for, any oil marked under regulation 5 (marking required for delivery without payment of duty), such oil is not to be used as fuel for any engine, motor or other machinery or as heating fuel.