Your serial number indicates that your Smith and Wesson model 59 was made in the year 1975.
With the serial number that you have provided,your Smith and Wesson model 39-2 was made in 1975-1976.
1975-1976
1975
1975-76
300-500 depending on if "mint" is really "mint"
@ 1975/6
1975-1977
1975
C. 1975, value around $300. sales@countrygunsmith.net nib 350.00 exc 275.00
Late 1974 to early 1975.
@ 1975