It sounds like an ex-sniper.
I don't mean to offend you, just want to make sure that you know where to look for plugged/welded holes on 1935 rifle.
The mounting holes should be on the shank (three on each side), unless the rifle was re-barreled at some point.
If you have a 1935 Tula with the "cn" Sniper Accuracy proofs but no visible holes in the receiver, you have one of 2 things.
First, as mentioned, this could be an "ex"-sniper with the plugged holes in the receiver. As shown in the photographs, when examined carefully and closely the 3 holes on either side will be visible. A '35 PE top-mount rifle with a good shootable bore is definitely worth picking up, and the availability of current Ukrainian production scope and mount setups makes these a good candidate for restoration to original and most historically significant combat sniper configuration.
The second thing such a rifle could be is one of the Sniper Accuracy proofed rifles that were produced as snipers or passed the accuracy test for snipers, but for some reason were never drilled and tapped and fitted with a scope setup. The exact reason this was done isn't known, but the Soviets had some purpose - perhaps several different reasons - for manufacturing these rifles, which can be found with dates from the early 1930's up to 1944. These rifles are not real common, and early dates like this are especially scarce. Again, one of these in good condition with a decent bore is a very collectable item that is definitely worth picking up and adding to one's collection.