The MSS SP-55, Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components - Visual Method for Evaluation of Surface Irregularities, was originally adopted in 1961. It was developed for the purpose of providing the industry with a uniform means for identifj4ng various types of casting surface irregularities.A set of 60 reference photographs illustrating these casting surface irregularities is included in the standard to permit a visual comparison of an actual casting surface with the reference photographs for the purpose of establishing acceptablehnacceptle casting surface irregularities.