Wow, it's nice to see how many ways there are to do something. I used 2 different ways to remove the rear sight on 2 different rifles, one a AMD-63 the other an AK-74.
AMD-63: With the rear sight base clamped in a vise, I used a screwdriver that fits the slot in front of the rear sight, you can see just a small portion of the spring. I depress the spring (heavy tension), the rear sight is then pushed down and rearward to remove. Installation is the reverse.
AK-74: The above wouldn't work because there wasn't any portion of the spring showing in the slot. So I used the same method but didn't use a screwdriver, I used a wide handle punch (T-handle type) pushed on the rear sight, just forward of where the small sight retaining side pins are located. Again, pushed down and rearward to remove. Installation is the reverse.
I wonder if there is a factory method of doing this job. That spring tension is "HEAVY DUTY".
Oh, as a side note the little dimple on the rear sight spring is to locate the spring in a detent so it won't move.