/usr/include/simgear/props/ is in libsimgear-dev 3.0.0-6+b2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/simgear/props/AtomicChangeListener.hxx
/usr/include/simgear/props/ExtendedPropertyAdapter.hxx
/usr/include/simgear/props/PropertyBasedElement.hxx
/usr/include/simgear/props/PropertyBasedMgr.hxx
/usr/include/simgear/props/PropertyInterpolationMgr.hxx
/usr/include/simgear/props/PropertyInterpolator.hxx
/usr/include/simgear/props/condition.hxx
/usr/include/simgear/props/easing_functions.hxx
/usr/include/simgear/props/propertyObject.hxx
/usr/include/simgear/props/props.hxx
/usr/include/simgear/props/props_io.hxx
/usr/include/simgear/props/propsfwd.hxx
/usr/include/simgear/props/tiedpropertylist.hxx
/usr/include/simgear/props/vectorPropTemplates.hxx