Listed as "SW 686 HAMMER, TRIGGER, CYLINDER RELEASE ASSEMBLIES," this is demilled 686 frame with all of the lockwork for $50. I ordered one 3 years ago and this is the first time they've had them in stock since. They don't state which engineering change they are. The one that I received was from a 686-3. the picture on the current listing appears to be a 686-2.
https://www.robertrtg.com/store/pc/viewPrd.asp?idproduct=3240
https://www.robertrtg.com/store/pc/viewPrd.asp?idproduct=3240