Every employer or user referred to in subregulation (1) shall be in possession of a certificate in a form acceptable to the chief inspector, which has been issued by an approved inspection authority and in which it is certified that the electrical machinery referred to in subregulation (2) has been manufactured and tested for the groups of dangerous articles in accordance with the relevant health and safety standard incorporated into these Regulations under section 44 of the Act: Provided that in lieu of such certificate an inspector may approve permanent labelling on such machinery, which label shall contain all the relevant information.