Ex-snipers will have the old screw holes visible on the inside of the receiver wall on the left opposite the bolt. That's about the only thing that will be consistent with all of them. They didn't simply line out the scope serial number on most, they ground it off. The screw holes were filled and welded over, polished and then re-blued during the arsenal process. Tiger striped stocks are laminate stocks and are post war additions. They would not be original to a 1943 rifle, they are also not exclusive to snipers, they used them as replacements on all rifles that had bad stocks.
Pre-war rifles will all be "finished". 1942 and 1943 rifles will usually not be well finished. They look rough. A 1942 or 1943 rifle that looks better than most may indicate it was a sniper but you need to check inside the receiver for the mount holes. Sniper rifles were indeed selected for accuracy and they were finished a bit further than the run of the mill rifles. That's how I got mine, completely by accident. I was looking at a dozen or so and this one had a nicely finished receiver as opposed to badly finished receivers on the rest. It wasn't until I got it home and got the cosmoline out of it that I found the holes for the scope mount.