If the certificates still do not identify when Robert DICKSON died, then you can apply online, to NSW State Records, for the intestate estate case papers, for him. Details previously posted to you. The charge is:
A $15.00 Admin fee + postage also applies.
This paperwork, should state where and when he died.
NRS 13538, Curator of Intestate Estate: Case Papers, 1821-1913.
The Case Papers provide details such as: money owed by the deceased, creditors and petitions from the Curator of Intestates to the Supreme Court relating to the administration of the estate, affidavits of death newspaper cuttings and in certain cases personal correspondence. Files may also provide information that relates to the nature and locality of death or the occupation of the deceased. The index records the name of deceased, alias (if any), district, date of order, file number and item number.