This part of IEC 60424 gives guidance on allowable limits of surface irregularities of ferrite cores. This standard is considered as a general specification useful in the negotiation between ferrite core manufacturers and customers about surface irregularities.
DS/EN 60424-1:2000 history
2000DS/EN 60424-1:2000 Ferrite cores - Guide on the limits of surface irregularities - Part 1: General specification