These cancellations on North Borneo BMA stamps are rather unusual and perhaps uncommon. It is rather faint in violet and should read AIR FORCE P.O. 234. They were from Labuan.
From the 2 enhanced montage of stamps, one can probably see most of this cancellation. The date was 1 FE 46 and towards the lower part one could see a 234. This would correlate with the Labuan Air Force P. O. 234 cancellation and according to Ted Proud and Stephenson Stobbs was used between 12 JU 45 and 1 AP 46. Proud gives this 350 points in terms of value and that of course that depends on the quality of the cancellation. The concurrent Air Force Post Office No 56 cancellation which was probably only used in September and October 1945 is very rare and has been allocated 2000 points by Proud.
Further research shows that AFPO 234 is probably not that uncommon as various covers are recorded as well as cancellations on Sarawak BMA stamps as well. Most of these are probably philatelic in origin, as with this short set. We can assume that most of these material would naturally reside in Australia.
Bristol Beaufighter planes 93 Squadron
The first landing by the Australian Army occurred on 10 June 1945. Due to the lack of suitable ground, the first aircraft of 93 Squadron RAAF did not arrive until July 1945 and the remainder came to Labuan on 5 August 1945. One of the unfortunate consequences of their actions was the sinking of Mia Moanai, the private yacht of the Rajah of Sarawak. There were further mishaps and the squadron was downgraded towards the end of December 1945 and then transferred by March 1946 to Japan. The squadron was disbanded on 22 August 1946.