Symbol 5992 from IEC 60417 - Title/Meaning: Locking, numerals; num-lock Function/description: To indicate numerical locking status, locked and unlocked for typing numerical characters.
Additional information: 
This symbol should not be used on a key. See also ISO 7000-2012.
The symbol element inside this graphical symbol may vary and usually correspond to the letter symbol for 1 or 9
Published in: 3C/1499/FDIS, 3C/1511/RVD
Own work using: iso.org/obp/graphics/grs/11508f48-8e46-4b50-9d63-151fcb39841d 200.png
Vectorization:  Mrmw