I think the 686-4 is from the early to mid 90's? The yoke head and screw on this gun are the 45 degree type - this not the spring pin type of retention screw system with a "flat" yoke head that I think came later.
I know there are a couple/few different type of yoke heads/screw types in 686's (45 degree and flat yoke heads and pointy or flat, with/without spring screws, etc), not sure the order in which they were produced. I have a no dash 686 with a flat yoke head and flat end screw but this used gun has been back to the factory at some point (marked "M") so the yoke system might not be original.
This damaged 686-4 is a round butt pre-lock with just a plain old 45 degree pointy screw that cut through the 45 degree yoke from speed reloading. When I reload I use my strong hand (right hand) to reach for the speedloader, so the gun is switched to weakhand.
It has been sent back to Smith last week ... guess it is a wait and see what happens situation now. Any clue as to Smith's current turn-around time?