Whisper Key Lock, Left Hand:  This lock is place below the whisper key and activated by the left thumb. 
Catalog Number:  31
Available On:  Models 601, 660, 101, 201, I, II, III, & IV
Standard Included On: 
Conflicts With:  While it does not actually conflict, it is not recommended at the same time as right hand whisper key locks. 
Required Deletion:  Models 601, 660, 101, 201, I, II, III: Delete Right Hand Whisper Key Lock, Type II (39)