Hi Lorna Under Robert Fairbairn it is written, ISO RM, that could have a number of meanings, perhaps you know which?
As for being related to Sir William, who knows? But I do remember the wow factor when the Fairbairn name had been mentioned and being very young at the time, I later related that to the Minister Sir David Fairbairn or James or some such relly. My grandmother was the niece of Beatrice Florence (nee Allan) Fairbairn. They (and George Oscar in Moree) died in NSW too, where Florence originally came from.
It also might help if we knew who John Seccombe is/was? He married Janet Ainslie Fairbairn. Later divorced, but issue of three sons, cases only go to 1923 for NSW? I've also been throuigh the NLA. My guess is that Janet Ainslie is still about under a new married name.