Mich. Comp. Laws § 290.605

Sec. 5. In addition to the state primary standards provided for in section 4, this state shall supply at least 1 complete set of copies of the state primary standards to be kept in the weights and measures laboratory of the department to be known as secondary standards. This state shall also supply field standards and equipment as may be found necessary to carry out this act. The secondary standards shall be verified upon their initial receipt and as often thereafter as the director considers necessary. The field standards shall be verified upon their initial receipt and at least once every 5 years thereafter. The secondary standards shall be verified by direct comparison with the state primary standards. The field standards shall be verified by direct comparison with the secondary standards.