Symbol 6264 from IEC 60417 - Title/Meaning: Position of use, vertical Function/description: To indicate that the instrument to be used with the dial vertical.
Additional information: 
See also symbol IEC 60417-6265 and IEC 60417-6266.
IEC 60051-1 provides technical details.
Own work using: iso.org/obp/graphics/grs/94f6fd08-9fd0-4717-8440-780951356fbc 200.png
Vectorization:  Mrmw