Throughout much of its history, Shimano has had an abiding fascination with spring-loading the cables that operate its derailleurs. This entails either including a sprung cable stop or a sprung cable clamp.
Shimano's hard working Marketing Department has justified this in a number of ways:
I never really bought into the first two explanations - but I thoroughly agreed with the third one.
These derailleurs with sprung cable mounting systems were surprisingly nice to use with a pleasing, supple, fluid, change.
Shimano Lark II (LK10) 1977?
Shimano Eagle II (EG10) 1977?
Shimano 400 FF (DC400F) 1977?