[QUOTE=Moose668;139470525 . . . am trying to figure out exactly what it is and when it was built.
Model: 36-1
Serial number: J109XXX
38 Special
3" barrel
fixed sight[/QUOTE]
Your S&W Model 36-1 is a Chiefs Special chambered in the popular .38 Special with a 3" Heavy barrel that was introduced in the Fall of 1966. It came in either a round or square butt . . . yours has the square butt. The combination of the heavy barrel and square butt is believed by some of us to have the perfect balance and recoil control.
Based on the serial number it was likely built in 1973.