This International Standard specifies the dimensions of triangular indexable (throwaway) hardmetal (cemented car-bide) inserts intended to be mounted mechanically, and not by brazing, on milling cutters.
Square inserts are dealt with in ISO 3365/1.
IS 11523 Pt.2-1986 history
1986IS 11523 Pt.2-1986 Dimensions of indexable (disposable) carbide inserts for milling cutters Part 2 Triangular inserts