In this Part of this Act -
the expression "industrial assurance company" means an assurance company which carries on industrial assurance business;
the word "collector" means a person, howsoever remunerated, who makes house to house visits for the purpose of receiving premiums payable on policies of industrial assurance and includes a deputy of or substitute for any such person, and also includes a person who holds' any interest in a collecting book;
the expression "collecting book" means any book or document issued by an industrial assurance company and in the custody of a collector in which payments of premiums on foot of policies of industrial assurance are entered;
the expression "premium receipt book" means any book or document in which acknowledgments of the receipt of premiums payable in respect of a policy of industrial assurance are entered.