According to the latest issue of Reveille, the NSW RSL magazine, their Last Post lists the following:
Peter John O'Brien, R42081. National Archives shows that Peter was a member of the Jan 57 intake at Nirimba.
He did his Vietnam service in HMAS Queenborough in 1963.
He also served in Quiberon, Gascoyne and the last entry up until 1970, was Platypus.
I never served with Peter but sad to see another MOBI finish his watch.
RIP Peter