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 96% full with much of the original finish with patina & scratches from use and the tang Is 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 well below the liners closed, good snap and tight lockup open. EX condition.