Originally designed for the infamous RPG-7 rocket launcher, the PGO-7 is a 2.8x optic with PSO style illuminated reticule for low light shooting. Unlike most PSO's which have a red bulb, it seems that the PGO bulb is commonly amber or pale yellow.
While not intended to be used on AK's there is a famous photograph of a PGO-7 mounted to an AKS-74N from the Russian-Afghanistan war in the 80's. There has been some question as to whether the optic can be properly zeroed to an AK or if it was just used as a spotting scope.
As a matter of fact the PGO can indeed be zeroed to an AK. Windage is typical being on the side but elevation is less obvious and is under the optic instead of on top. By loosening the 3 outer screws, you can use a screw driver to move the reticule up and down.
I have found that the boresight cross is too high to bring on target at 100m but that the 2 range line where it intersects with the double center line can be used for a 100m zero.
Russian and Bulgarian PGO-7V
Chinese PGO (In green).
Note that the Chinese PGO will NOT FIT an AK rail. While similar you can see the base is smaller than the standard Soviet style mount and it will not slide onto AK or SVD rails.
On the SLR105 /AKS-74N
The optic sits directly to the left of the receiver and is somewhat awkward to use, but it can be effectively employed for aimed shooting at longer ranges. I would not consider this a CQB optic by any stretch but under other circumstances it could be useful.