S marking?...

I took the grips off my S/42 this morning,and was so happy to find out that they match the serial # of the gun (I was too chicken to take em off before now because I was afarid they woulden't match). I also found that the right grip has a sidways S marking does anyone know if that means anything? I was just curious. the Luger has no letter prefix, So I don't know what it means!

HELP!!!!! IT'S DRIVING ME CRAZY!!!