Symbol 5006 from IEC 60417 - Title/Meaning: Minus; negative polarity Function/description: To identify the negative terminal(s) of equipment which is used with, or generates direct current.
Additional information: 
The meaning of this graphical symbol depends upon its orientation
Published in: First edition, 1973
Own work using: iso.org/obp/graphics/grs/df0b671b-83f4-4da9-9ead-2a332e3ba8c0 200.png
Vectorization:  Mrmw