An enigmatic character. The ADRIC rolls show he was with AIF. This is the only officer "F W Harper" in AIF. There is a Frederick W Harper who was discharged from AIF in Set 1917 as a private, unfit for military service (and no record of him rejoining AIF).
I think our man is the older of the two possible, and that RIC year of birth of 1891 was wrong, probably as mistranscription. He appears to have been illegitimate, son of Maria Fox
1872 Apr Born Halifax, Yorks. He says 42.5 years when he enlists. The medical reports in 1919 suggest born 1864. His age in 1918 of 46 is crossed out and 55 inserted. The probability is that he was born Frederick William Fox in Bradford Jul/Sep 1862. This would suggest he took a straight 10 years off his age on enlisting. RIC has 10 Jan 1891 as his dob
1894 Married in Broken Hill, New South Wales to Sophy Bright (1871–1947)
1915 Oct 15. Enlists in AIF, he is a widower aged 42, son Hugh Garrod Harper, served previously in 15th Hussars and purchased a discharge. A Clerk
1917 Jan 1. Commissioned 2nd Lt in ANZAC Provost Corps
1917 Apr 22. Promoted Lt
1917 Jun 1. Promoted Quartermaster
1919 Jan 4. Leaves UK on troopship to return to Australia
1919 Jun 30 Appointment terminated
1920 Dec 13. Joined ADRIC with service no 1244 . Posted to L. Coy. Joined with J E F Claughton
1921 May 14. Posted to Depot Coy.
1921 Nov 15 to 19 Dec. In Stevens Hospital
1921 Dec 31. "Services dispensed with" . Late in the day, he must have been very bad
1924 Dec 12. In Prince of Wales Hospital Randwick.NSW
1939 Electoral register in Brisbane, with Sophy
1942 Aug 7 Died (from Army record) This was in Queensland and gives his father as Samuel Harper and mother as Maria Fox (BMB shows they married 1864 in St Asaph in Wales). I cannot find them in 1871 or later censuses. Shipping records do not exist for this period, so I cannot establish when they went to Australia.
The younger man who was discharged in Sep 1917 as a Private
1917 Apr 2 Enlisted
1917 Sep 14 Discharged "unfit"