I just inherited my fathers 439 , looks to be unfired with the original box, for some unknown reason my father decided to tinker with the rear sight and the only thing left is the base that is still sitting in the dove tail, Do I need to get this directly from S&W ? Im not even sure what the parts look like that are missing, but seeing the holes in the base I imagine there is a pin and the ramp and possibly a spring ?

Hi Mike here is a schematic breakdown for a 39 which maybe used for your 439 for parts references.

http://stevespages.com/ipb-sandw-39.html

586L-Frame