Guten Morgan mein Herr
Which of the two types of sights do you have? The one on the left is an earlier gun. The one on the right should be a 686-4 gun.

Also, be careful when ordering a complete rear sight. They come in different heights(the depth of the square notch). Look close at the picture!

The "-#" is the latest engineering change made to the gun which helps date the gun.
I hope this helps? jcelect