The quick visual ID for an SVT-38 mag is a cup style floorplate. IIRC, there is also a takedown pin on the side not the bottom.
The other markings are still being decoded by collectors and linguists much smarter than normal shooters. The two things that matter are the year code, and the five-point star for the Tula arsenal. Since the end of the LGR, the serial number on the left side of the reciever ring is less important for the average guy. It does however have meaning to the collectors, who are figuring out production batches and numbering ranges.