Straight bolt handle - Earliest C models up to 1961 when bolt handles became curved : 1949 -1960 Here are some known facts as they pertain to your rifle: Until 1956, the rear sight was soldered with the first year knurled windage adustmentsġ960 5 M/M Cal & Made in USA added to pump tubeġ961 saw evolution of the bolt from straight to curved to pear shaped with hole (eventually removed 1975)ġ963 with a switch from the hold down safety to the rocker safetyġ964 changed the front sight to a forward ramp style.ġ964 Inspection dates were stamped on left side of receiver (Backwards and alphabetically) My Silver Streak manufactured between 1956 1958 hope this helps.