The IBM 1311 hard drive
Only two years after creating the RAMAC 305, IBM released the 1311, the first storage system that used "flying heads" on actuator arms to read and write data to its 50 24-inch magnetic platters. The 1311's head and actuator arm assembly looked something like a bread-slicing machine turned on its side because each drive platter had its own read/write head.
Photo courtesy of IBM Archives.