Conventional hammer spur?
Shrouded hammer spur with the top of the hammer visible??
Or no visable hammer?
Fixed sights or adjustable sights?
Anyway, the J serial number prefix was used from 1969 to 1983.
On Model 36, 37, 38, 49, and 50.
The date would be 1976-77.
But the exact model cannot be determined without more complete information.
More then likely though it is a standard 3" Model 36 Chiefs Special.
rc