So those ridges did have a name
In a previous version of this board, I had asked about the ridges one could find on Capitol-related 45's. I finally found the answer, after reading one of my old Beatology magazines:The singles also had something new to most Americans - a slip guard consisting of 360 interlocking serations surrounding the label. Although the tiny groove appeared to be an innovation of Capitol, several British labels jad been pressing discs with slip guards for years. By coincidence, Capitol had re-tooled its pressing plants for slip guards at the beginning of the month, so the Apple singles were among the first Capitol manufactured singles to take on the new look.