3 Pa.C.S. § 4107

In addition to the State standards provided for in section 4106 (relating to State standards of weight and measure), there shall be supplied by the Commonwealth at least one complete set of copies of the State standards to be kept in the office or laboratory of the bureau and to be known as "office standards" and also such "field standards" and such equipment as may be found necessary to carry out the provisions of this chapter. The office standards and field standards shall be verified upon their initial receipt and, at least once each year thereafter, the office standards by direct comparison with the State standards and the field standards by comparison with the office standards.