This 49 SKS shows several traits of an early build. Before this, I only thought that if there was no rivet on the magazine, cleaning rod nubs being parallel and if there was a 1 in the serial number, that they were sans serif. I have noticed several other features since then.
1 - Magazine without a rivet.
2 - Cleaning rod nubs are parallel.
3 - If there is a 1 in the serial number they are all sans serif. Although Sean's does not have a 1, an example of mine is shown.
New observations.
4 - No knurls on magazine release and safety lever.
5 - Sling bracket is wider than later SKS. Will show comparison.
6 - Op rod is beveled on 2 sides and has a OTK marking.
7 - Stock trap door and comparison
8 - No marking on the front sight.
Other than missing the knurls on the safety lever and magazine release plus the wider sling mount, my ЮE 1217 has all the other features.