Smith and Wesson began listing serial numbers in 1984 with a three letter prefix to there serial numbers.So you should be able to identify the year of manufacture by the 3 letter prefix and then the following number.Smith and Wesson began production of the model 4046 in 1991,and discontinued this model in 1999.The Smith and Wesson model 4046 Tactical was made from 2000-2002.I hope you find this of interest.
K 7981 smith&wesson
1969
1880
1961
@ 1967
1948
1947
76-77
1977
1978
1977.
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