No civilian/commercial proofmarks at all. These gothic letters with crowns above were the personal marks of German military inspectors up to 1918. So your action was made originally as a WW1 military Gewehr 98 rifle by the Mauser factory in Oberndorf am Neckar. The military rifles were not proof fired individually, just samples from production batches were checked. The names of the inspectors behind the letters are forgotten more than 100 years later. But as the order for applying the stamps is still known, we may know from the position of the 3 stamps on receiver ring what was inspected: Here “G” checked the receiver for proper dimensions and hardening, “E” checked both the barrel itself and the fitting and headspacing to the action.