This is a close up of the left side of the frame. It shows the "1" serial number and an eagle over a 359, Walther Military acceptance stamp.
To show you the same stamp wasn't used one each Walther "Nazis" Military acceptance stamp, please see photos 8, 13, 14, 15, 16 and 22. Notice each is different in appearance, depth and clearness. This proves it wasn't the same stamp used or done in the same part of the factory.