Serial number is printed on the scale and a certificate of traceability is included

The hydrometer meets or exceeds the requirements in ASTM specification E100, and it is calibrated to ASTM specification E126 to ensure accuracy. The certificate of traceability indicates that the hydrometers are manufactured using devices calibrated using NIST traceable standards. The ballast is made from steel pellets and a binder, and it is free of heavier metals.