N.H. Rev. Stat. Ann. § 438:5

In addition to the state standards provided for in RSA 438:4, there shall be supplied by the state such "field standards" and such equipment as may be found necessary to carry out the provisions of this chapter. The field standards shall be verified upon their initial receipt and at intervals, as recommended by the National Conference on Weights and Measures Handbook 105 series pursuant to RSA 438:8, IV, thereafter by comparison with the state standards or standards of NIST recognized or accredited laboratories.