Symbol 5387 from IEC 60417 - Title/Meaning: Beam limiting device with separate opening of the shutters Function/description: To identify controls for opening one set of shutters or a single shutter of a beam limiting device.
Additional information: 
The controlled shutters are shown in thicker lines
Published in: Supplement G, 1985
Own work using: iso.org/obp/graphics/grs/6dc00363-8a2c-4259-a4ff-7ccbdc6349f7 200.png
Vectorization:  Mrmw