(a) Each person, firm or corporation engaged in the business of buying milk or cream on the basis of the percentage of butterfat contained therein, as determined by any test approved by the Milk Regulation Board of samples taken in accordance with the regulations of the Milk Regulation Board, shall have the samples taken by a person holding a license to sample milk or cream.
(b) Each licensed sampler shall carry upon his person or post his license in plain view in the plant in which he is employed.
(c) The commissioner may revoke such license for failure to carry or post it as required under this section or for any other just cause. Each such license which has been revoked shall be returned to the commissioner.