/usr/include/Inventor/projectors/ is in libcoin80-dev 3.1.4~abc9f50-4ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/Inventor/projectors/SbCylinderPlaneProjector.h
/usr/include/Inventor/projectors/SbCylinderProjector.h
/usr/include/Inventor/projectors/SbCylinderSectionProjector.h
/usr/include/Inventor/projectors/SbCylinderSheetProjector.h
/usr/include/Inventor/projectors/SbLineProjector.h
/usr/include/Inventor/projectors/SbPlaneProjector.h
/usr/include/Inventor/projectors/SbProjector.h
/usr/include/Inventor/projectors/SbProjectors.h
/usr/include/Inventor/projectors/SbSpherePlaneProjector.h
/usr/include/Inventor/projectors/SbSphereProjector.h
/usr/include/Inventor/projectors/SbSphereSectionProjector.h
/usr/include/Inventor/projectors/SbSphereSheetProjector.h