I will stick my neck out and say 1980 ish. The first ones (1973 and maybe a little beyond) started the serial numbers and had non-stainless steel blades. At some point they quit serializing them and I think long before 1990. There are brazillions of these 153s; they made them from 1973 until the bankruptcy in 2004.
Cal Pruett is my name; trad knives is my game. Always interested pre-war Schrade CutCo knives & always have dozens others eclectic mix to trade/sell