Hi there,
Have you approached the NSW State Records office directly to ask them about these records ....
You may find that the records you are seeking are in the process of being indexed/catalogued etc. Perhaps they already have the handwritten book that would have been used by the Prison's clerical staff in 1917 as their local index... if so there will be clues to help located his particular record at the Archives.
Access is available to the public for many of their archives that I have not found on online indexes .... The staff are friendly and the rooms are well organised. It can take up to an hour for the retrieval system to bring a file to the counter after you request it, BUT once you have seen the size of their storeage facility at Kingswood you understand why.
NSW State Records Office
A Division of the Department of Services, Technology & Administration
PO Box 516, Kingswood, NSW 2747, Australia, Email: info (at) records.nsw.gov.au
http://www.records.nsw.gov.au/ (their phone and fax number are also displayed at the bottom of that welcome page) ...