Any appearance, application or act required to be made or done by any person before or to a Commissioner (other than an appearance of a party which is required for the purpose of his examination as a witness) may be made or done on behalf of such person by a legal practitioner or by an official of an Insurance Company or a registered Trade Union or by an Inspector appointed under sub-section (1) of Section 8 of the Factories Act, 1948 (63 of 1948), or under sub-section (1) of Section 5 of the Mines Act, 1952 (35 of 1952), or by any other officer specified by the State Government in this behalf, authorised in writing by such person, or, with the permission of the Commissioner, by any other person so authorised.