Sch 1 para 5 Marking
(1) All equipment and protective systems must be marked legibly and indelibly with the following minimum particulars— (a) name, registered trade name or registered trade mark, and address of the manufacturer; (b) UK marking ; (c) designation of series or type; (d) batch or serial number, if any; (e) year of construction; (f) the specific marking of explosion protection followed by the symbol of the equipment-group and category; (g) for equipment-group II, (i) the letter ‘G’ (concerning explosive atmospheres caused by gases, vapours or mists); or (ii) the letter ‘D’ (concerning explosive atmospheres caused by dust); or (iii) both the letter ‘G’ (concerning explosive atmospheres caused by gases, vapours or mists) and the letter ‘D’ (concerning explosive atmospheres caused by dust). (2) Furthermore, where necessary, they must also be marked with all information essential to their safe use.