N.H. Rev. Stat. Ann. § 438:4

Such 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 the state for use as state standards shall, when the same have been certified as being satisfactory for use as such by the National Institute of Standards and Technology, be the state standards of weight and measure. The state standards shall be kept in a safe and suitable place in the office or laboratory of the state bureau of weights and measures; they shall not be removed from the said office or laboratory except for repairs or for certification.