Sold Zeiss ZFK 4x25 scope radiation hazard decal, reproduction

Were these originally used for older PSO scopes that used irradiated elements to permanently illuminate the lens reticle?

I am not aware about any PSO scope that would use such as thing.
As far as i know there were PSO scopes that had IR source detection capability, but thats a different thing.
The only two combloc scopes that used the reticle ilumination by isotopes were ZFK and Romanian LPS scope.

I asked because I have one. Im not sure of it's origin but it was made in 1975. It's long since expired so the reticle isn't illuminated anymore.