230.2 Identification of Standard Reference Materials.§ 230.2 Identification of Standard Reference Materials.
The SRM's are listed by category in SP 260 and by sequential number in the supplements. The number uniquely identifies a particular SRM. Renewals are indicated by the addition of a letter to the original number. Thus, 11a is the first, 11b the second, and 11c the third renewal of SRM 11, Basic Open-Hearth Steel, 0.2 percent carbon. In this way, a particular number or number and letter always represent a material of fixed or approximately fixed composition.