Hi Darrin,
OK, see your point, however this was my logic based upon formation and unit orders, and based upon your desire to represent 10/48 Infantry Battalion
(AIF). This places the unit within a date range from March 1943 onwards (until the signage system changed in August 1944), as the unit did not 'go AIF' until about that date. (If you scratch the 'AIF' from the title, it date range could be Sept 42 onwards....)
10/48 Inf Bn arrived in NT as part of 3 Inf Bde in September 42, soon after amalgamation between 10 and 48 Inf Bns had taken place in August. Just before that, 10 Inf Bn had been in Sydney as part of 1 Inf Division prior to amalgamation with 48 Inf Bn - they are listed on 1 Div's ORBAT for 22 June 1942, with the unit sign 63 on a green background.
By end Dec 42, 10/48 Inf Bn had been transferred to 23 Aust Infantry Brigade, which was part of NT Force. (By then, 4 Div was in WA and well out of the picture).
The formation sign for NT Force/12 Aust Div came into existence in early 1943, and was promulgated by NT Force HQ as applying to all vehicles within the Force.
10/48 Inf Bn remained in NT Force until 1945, moving several times during that period: Nov 42 from 51.5 Mile to Fanny Bay; March 43 from Darwin Fortress to 37 Mile Camp; Nov 43 to Parap Camp; Dec 43 to 69 Mile Camp; March 44 back to Parap Camp, and May 44 to 67 Mile Camp, and so on.
So, the markings for 10/48 Inf Bn (AIF) have to post-date the Unit voting to 'go AIF', hence after March 1943. At that time they were (1) part of 23 Inf Bde and (2) with the higher formation of NT Force.
When the unit was posted to join 23 Inf Bde, they were allocated the unit sign of 53 on a red background, as per NT Force GS Instruction dated 15 December 1942. In early 1943, NT Force issued instructions that all vehs were to carry the buffalo over boomerang sign (and others were to be obliterated).
Hence, by March 1943 when the unit 'went AIF', the essential elements of the sign that come together for 10/48 Inf Bn were: 53 red background; Buffalo over boomerang.
As regards 82 on brown, this was indeed the marking for the 1st Battalion of the 3rd Brigade within an Infantry Division, but the actual application of same at unit level was also subject to a whole raft of other factors. And besides, 10/48 were, in theory, the 3rd Inf Bn within the 3rd Infantry Brigade within NT Force (23 Inf Bde had 7, 8, and 10/48 Bns), so in theory should have had the number '77' on the unit sign anyway. Why 53 on red? Hell, I don't know: some officer in higher HQ said so, that's why!
So, what you ultimately decide is up to you: it is your track, and what a truly magnificent job you are doing on it, too.
Regards
Mike