Here are some known facts as they pertain to your rifle:Straight bolt handle - Earliest C models up to 1961 when bolt handles became curved : 1949 -1960Rear Sight - sight held by small allen-head screw opposing two dimples on opposite side : 1956 - 1971 (earlier models featured permanently soldered rear sights with knurled windage knobs) Automatic Safety - Pre 1963 when rocker was introduced. 1949-1962Narrow Trigger Guard - 1959 and earlier (can't see it in your pic but there should be philips screws holding the trigger guard instead of rivets)Stock and Forearm - If 4 screws were used in place of roll pins on the forearm, then it indicates one of first two years of that model - along with thin "almost crude" stock and thin cylindrical forearm 1949-1951. Roll pins indicate 3rd year production onward. - 1952 onPartridge-style front sight with vertical rear face - Incorporated 2-3 years after introduction of the C model : 1951-1964Simple Markings - the words "5mm Cal" and "Made in USA" on opposite side introduced in 1960. Absent those inscriptions 1949-1959High Comb Stock - 1949-1958 Lowered in 1959I'd say the best guess given the info on hand is it's between a 1956 - 1958 model (Based on rear sight and high comb).TimVPilot
Finally found time to tinker and re-sealed this Silver and ran some Chrony numbers.The pump cup was so brittle that when I tried to flex it it just broke apart. Got the adaptor to replace the old style cup from Rick @ Precision.New poppet and stem. JSB 13.73 Diabolo 80degrees outside15 shots at 5 pumps= 551.95 average FPS, 9.29 FPE10 shots at 8 pumps= 655.2 FPS, 13.08 FPEDon't know if anybody is keeping a database for these old C's, but thought you might be interested.Thanks for all the help dating this beauty.