Symbol 5536 from IEC 60417 - Title/Meaning: Moisture Function/description: To identify an indicator for a moisture condensation condition within the equipment.
Additional information: 
The drop may be filled in
Published in: Supplement M, 1994
Own work using: iso.org/obp/graphics/grs/ddb7b894-287f-4672-9d67-28d49e93d620 200.png
Vectorization:  Mrmw