Kell strom Surface Protractor p/n 36D Universal Bubble propeller Protractor w/case Older Bubble Protractor previously used in Aircraft maint shop. Made by Kell-Strom Tool Company Universal Bubble Protractor 36D , p/n KS and Federal Mfg code . Calibration verified on . See pics. All markings and mechanisms work excellent. Some chips along the edges and Shop tool I.D.s etched on face