The Troemner Precision Analytical Mass Sets have tolerances 40% to 50% better than ANSI/ASTM E617 Class I and equal to exceeding OIML Class E2 standards. All weights are highly polished.
The 500 mg down to 50mg weights are 304 stainless steel. Weights below 50mg are flat aluminum weights.
All weights are calibrated by laboratories that are accredited by the NIST-administrered National Voluntary Laboratory Accreditation Program (NVLAP). Troemner is the only private mass metrology laboratory in the world accredited for E1 measurements with uncertainties at 1/3 the E1 tolerance. Certificates are not included.