Mont. Code Ann. § 30-12-103

Those weights and measures in conformity with the standards of the United States as have been supplied to the state by the federal government or otherwise obtained by this state for use as state standards are, when they have been certified as being satisfactory for use as such by the national institute of standards and technology, the state standards of weight and measure. The state standards must be kept in a safe and suitable place in the office or laboratory of the department. They may not be removed from there except for repairs or for certification.