SDCL § 37-20-4: Verification and sealing of working standards and field standards.

The division shall verify working standards at least once each five years and the field standards at least once each year. The working standards shall be verified by direct comparison with state reference standards, and the field standards by comparison with the working standards. If found accurate by these tests, the field and working standards shall be sealed by stamping the letters "S. D." and the last two figures of the year on them with seals which the secretary of the Department of Public Safety has and keeps for that purpose.