KABAR Lever Black Jigged synthetic Transitional Square lever vintage automatic knife

KABAR Lever Black Jigged synthetic Transitional Square lever vintage automatic knife pattern # 51105 made by Union Cutlery Co of Olean, NY sometime between 1920 and 1940. This is a transitional knife between the early teardrop lever and the later grooved square lever. They realized that the new smaller lever needed grooves to make it easier to operate and I think that change was made around 1932. The knife measures 4 9/16 inches closed and 7 7/8 inches open with thick brass liners and nickel silver bolsters and lever. The saber ground blade is 90% full and shiny and looks to have been professionally cleaned with the tang clearly stamped KA-BAR and the backside reads UNION CUT CO OLEAN, NY USA. The scales are black jigged synthetic material and are in excellent condition. The knife works well with blade tip a hair above the liners closed, good snap and tight lockup open. VG+ condition.