I would guess mid 70's, but I do not have a book here to check. Post the question here http://smith-wessonforum.com/eve and you will have an answer quickly and also some good reading.
1980
No serial number provided.
No serial number provided.
No serial number = no way to answer.
Need the serial number
No serial number provided.
K 7981 smith&wesson
You will need to add the model of Smith and Wesson to your serial number to get the correct year of manufacture.
1978
y
THA7110
@1971