The actual crosshair itself is custom-made, not built off a real scope reticle. However, the rangefinder was indeed taken from a PSO-1 scope.

*LOL Good Find*

Good fine, the time of its introduction around 1964.

Also, the PSO-1 pattern range-finding reticle. The bottom-left corner can be used to determine the distance from a 1.9 m tall target.

This I do believe is the PSO-1 which was specifically designed for the SVD as a telescopic sight for military designated marksman activities. The current version of the sight is the PSO-1M2. This telescopic sight is different from the original PSO-1 only in that it lacks the now obsolete infrared detector.