Every milk plant, creamery, shipping station or other factory or person or agent receiving, buying or paying for milk, cream or other dairy products on the basis of butterfat content, shall have in its employ at least one licensed weighman and sampler who shall supervise and be responsible for accurate weights and representative samples of all milk or cream received and paid for on the basis of weight and butterfat content. The license shall be issued by the Commissioner of Agriculture or his authorized agent upon receipt of a properly executed application form and upon the passing satisfactorily of an examination prescribed by the Commissioner. This license shall be valid for the term of one year and shall be revoked by the Commissioner upon evidence that the licensee has failed to comply with the rules and regulations under which the license was granted. Unless revoked this license shall be renewed annually upon application from the licensee.