Symbol 2013 from ISO 7000 - Title/Meaning: Level 3 select Function/description: To identify the control to select the set of characters or functions allocated to the level 3 of the keyboard in the currently active group.
Additional information: 
The meaning of the symbol depends on its orientation.
Own work using: iso.org/obp/graphics/grs/162900d3-15f7-4c85-8490-b548c1ad4f0a 200.png
Vectorization:  Mrmw