Smith and Wesson manufacture guns and firearms. They are the official guns that are used by the FBI, but are also standard issue to other police and armed forces.
K 7981 smith&wesson
1961
1969
@ 1967
1880
1948
1980
1954-1970
1947
76-77
Standard Catalog of Smith and Wesson, 3rd ed. might have the answer.
1992-1994