Amazing how much technology can change in a relatively short amount of time.

“These disks are mounted so as to rotate about a vertical axis, with a spacing of three tenths of an inch between disks. This spacing permits two magnetic heads to be positioned to any one of the 100 concentric tracks which are available on each side of each disk. Each track contains 500 alphanumeric characters. Total storage capacity: 5,000,000 characters. The two recording heads are mounted in a pair of arms which are moved, by a feed-back control system, in a radial direction to straddle a selected disk.”