Symbol 5973 from IEC 60417 - Title/Meaning: Mirror contact Function/description: To identify a normally closed auxiliary contact which cannot be in closed position simultaneously with the normally open main contact, not even during abnormal conditions like welding of the main contact.
Additional information: 
Published in: IEC 60417 database
Own work using: iso.org/obp/graphics/grs/4b3f6729-6ce1-4ae8-acc2-70bf1d94a17c 200.png
Vectorization:  Mrmw