Symbol 5020 from IEC 60417 - Title/Meaning: Frame or chassis Function/description: To identify the frame or chassis terminal.
Additional information: 
Published in: Supplement C, 1977
Own work using: iso.org/obp/graphics/grs/5393d352-ff14-4547-b030-cd4e4757e1f0 200.png
Vectorization:  Mrmw