Symbol 0541 from ISO 7000 - Title/Meaning: Variability with a preset starting point 
Function/description: To identify controls which directly or indirectly vary any given physical value, this value increasing in the direction of the taper rise, with defined starting position marked (for example, by a ratchet stop).
Own work using: iso.org/obp/graphics/grs/5c53b78f-5608-440e-876f-75b342659bc4 200.png
Vectorization:  Mrmw