ISI International Scientific Industries Reel to Reel Tape Recorders

We know very little about International Scientific Industries ISI tape recorders.

An ad from 1957 describing their model 100 tape recorder states – here’s a revolutionary engineering approach to tape recording that utilizes a magnetic differential clutch and brake system, completely out-performing conventional types. Through isimetric drive, the use of mechanical servo-feed-back system with magnetic differential automatically applies the correct torque to the supply and pick up reels thus maintaining constant tape tension and stability whether in play- record position or in fast-forward or rewind.

All very fancy talk for a tape recorder priced at $465 in 1957.