hi, my book shows early j frame numbers 1950-1969 from 1-786544
and 1962 ended with 295000
1969 ended with 786544.
that is as specific as it gets in my book.
I would guess 1968 or 1969 production.
In 1969 they also went with a prefix before the serial number and gave the models the number in the crane area if I understand correctly.