Complex sentence: The origin of the third kiwi cloak used to cover Bennington's coffin is uncertain, but had been used previously to repartriate the remains of New Zealanders who died abroad back to their homeland.
Split into simpler sentences: The origin of the third kiwi cloak used to cover Bennington's coffin is uncertain. The third cloak had been used previously to repartriate the remains of New Zealanders who died abroad back to their homeland.