I found this on line I hope it helps.
K Series K Frames (Adjustable Sight Models)
K101 – K614……………......1946
K615 – K18,731…………....1947
K18,732 – K73,121……..…1948
K73,122 – K84,149……..…1949
K84,150 – K104,047…...1950
K104,048 – K136,690...1951
K136,691 – K175,637...1952
K175,638 – K210,095...1953
K210,096 – K231,255...1954
K231,256 – K266,154...1955
K266,155 – K288,988...1956
K288,989 – K317,822...1957
K317,823 – K350,547...1958
K350,548 – K386,804...1959
K386,805 – K429,894...1960
K429,895 – K468,098...1961
K468,099 – K515,478...1962
K515,479 – K553,999....1963
K555,000 – K605.877....1964
K605,878 – K658.986....1965
K658,987 – K715,996....1966
K715,997 – K779.162....1967
K779,163 – K848,781....1968
K848,782 – K946,391....1969
K946,382 – K999,999....1970
1K1 – 1K39,500.........1970
2K1 – 2K22.037.........1970
1K39,501 – 1K999,999...1971
2K22,038 – 2K55,996....1971
3K1 – 3K73,962.........1971
2K55,997 – 2K99,999....1972
3K31,280 – 5K6,616.....1972
4K1 – 4K1,627..........1972
4K1,628 – 4K54,104.....1973
5K6,617 – 5K73,962.....1973
4K54,105 – 4K99,999....1974
5K73,963 – 6K58,917....1974
7K1 – 7K26,043.........1974
7K26,044 – 7K70,577....1975
6K98,918 – 8K20,763....1975
8K20,764 – 9K1.........1975
8K20,000 – 9K100,000...1975
9K1,001 – 9K99,999.....1976
10K001 – 24K9,999......1977
25K001 – 56K9,999......1978 – 79
57K001 – 91K6,800......1980
91K6,801 – 124K000.....1981
125K000 – 269K9,999....1982
270K000 – 311K273......1983
1980 Three-Letter Prefix Series Begins at AAA000
