The knob in Ø22 mm housing has a locking mechanism. The lock prevents unintentional adjustments.
The IMT series allows a very precise manual handling with up to 20 revolutions (50 dashes per revolution). The knob is used often with a multi-turn potentiometer (e.g. AL17/19).
Knob with 50 dashes
Revolution counter for 20 revolutions
With locking mechanism
For 3..6,35 mm shaft