Cocking piece is an RC, and the e marking is typical for parts made by Hermann Köhler, mostly used on bcd's.
As to the S markings, nobody knows for sure, but I can tell you that the majority of pre-war armorers parts have S markings. I personally think it's a holdover to the time when Simson was the only firm allowed to make spare components, and was continued even after it was unneeded (much like S/ code 98k manufacturers markings). I feel the S was meant to imply Simson, since they were allowed to make rifles as well (see S marked 98b's) in post WW1 Germany. These small S markings disappear around the same time S/ codes disappear.
It's all just theories as there really isn't a reason given in the surviving documents as to WHY the S/ codes were introduced.