Warner & Swasey Machine #3 Collet Pads
L” style bushings are used to adapt drill, boring bars and shank tools to any size in a standard turret or toolholder.
All “L” style bushings have set screw clearance holes opposite the slot and have a split with a flat on the O.D.
https://exacttooling.com/pages/lathe-toolholder-bushings-type-l/