From 1942: Disk in a plain-cover envelope, paper disk-label covers brand of disk. (The center of the disk has three holes, triangular, which was a non-slipping standard for audio re-broadcast disks.) John Cage & Kenneth Patchen: The City Wears a Slouch Hat [1943] The is evidently an original copy of the Columbia Workshop broadcast, recorded May 31, 1942 in Chicago. edge --> center (recording pattern), 1 track on each side, "START OUTSIDE"