I have a list of guns for sale from Germany. Many of the notes about the guns, written in German/ English mix, include the note SEM. What could that mean?

Suhler Einhak-Montage
Suhl Claw Mounts

SEM:
http://www.zp-einhakmontage.de/front_content.php?changelang=2

Thanks. That helps a lot.