O.T.: Simson Markings on a Karab 98 b
 

I recently acquired a rifle marked Karab 98 b on the left side rail. It has Weimar proofs and eagles with inspector numbers 6 and 43 under the eagles. There is stylized S on the right side of the receiver, but the receiver ring has no makers marks or date of manufacture. I know Simson made pistol and rifles for the Reichswehr. Were some of the rifles only marked with the letter S?