Hello Partner,
This topic can be I think be a bit complicated. So here goes:-
At the Haldane Reforms in 1908 British Volunteer Corps became The Territorial Forces. On the outbreak of war on 4 August 1914, almost immediately, TF units were invited to volunteer for Overseas Service. On 15 August 1914, the War Office issued instructions to separate those men who had signed up for Home Service only, and form them into reserve units. On 31 August, the formation of a reserve or 2nd Line unit was authorised for each 1st Line unit where 60 per cent or more of the men had volunteered for Overseas Service. So basically the 1/9 became the overseas service battalion of the 9th Royal Scots. The unit that remained for Home Service became the 2/9 the battalion. I am not too sure, but I believe that should a 2nd line battalion then volunteer for Overseas Service an 3rd battalion for Home Service was formed from the soldiers that did not opt to go abroad. I believe this system was abandoned later on in the war. These battalions were "old" Territorial battalions and not the New Kitchener Army battalions.
It may be pure chance that you selected that you selected the 9th Battalion Royal Scots, known at The Dandy Ninth, or to give them there proper name 9th (Highlanders)Royal Scots, wore the kilt. Yes, The Royal Scots were a Lowland Regiment and wore trews but the 9th wore a Hunting Stewart kilt, the Regimental tartan. (Neil Gilhooly wrote a history of this unit, still available.) The British Army wore uniform, but uniformity was at one time rare.
Hope this helps. Maybe there is someone out there who can explain more fully.
Yours,
Blackbob
