MBS stap on glock frame...meaning?

General Firearms Handguns - Semi Auto
1

The letters MBS are stamped on the frame of my G41, directly above the hook on the trigger guard on right side.
What do they mean?

2

Multiple (or modular some say) Back Straps.

3

According to Glock: “Modular Backstrap System”.

http://us.glock.com/technology/gen4

4

THANKS FELLAS! Learn something all the time here. I appreciate your time!!