From my knowledge they were all machined like that initially on both the SVT-38 and SVT-40. I don't think the notches were added until late 41/ early 42, because they were finding the scope mounts were sliding off and needed extra reinforcement, they were only added to SVT's that were test fired and had above average accuracy (circle k marking). During 1942, they stopped machining the rails into the receiver completely.
I'm sure Ratnik will be along to provide more accurate and detailed information.




























