Yesterday we had really good discussion under one of the posts and few guys doubted existence of scoped SKS.
Well, it all started in 1949, when Soviets run trials for “sniper carbine”. Few SKS models were submitted for trails (black and white pictures below, pictures from JIMJA).

Tula
Factory model

These were equipped with modified PU scope and had cheek risers installed on stock – I actually like those setups very much.
Rifles were submitted by TULA factory and OKB-180 factory.
Trails delivered rather disappointing results and these rifles never matured as production examples.

OKB-180 Factory Model

So SKS “sniper” idea was put on the back burner, until 90’s, when Yugoslav People’s Army, modified couple hundreds of Yugo SKS and equipped them with Zrak ON-2 Scope (calibrated for 7.62×39) – pictures in color (pictures from JIMJA).
Those rifles actually were actually used in service.

Yugoslavian SKS with scopes

Finally, Chinese were selling two versions of scoped SKS rifles in USA: Farmer’s Friend and Cowboy’s Companion (Navy Arms flyer).
Hope this helps.

Navy Arms Flyer