Hello,
a few points jump out at me..
The Medal Index Card indicates he served in a theatre of war. Indeed the one referred to as Archibald MacDonald would support this. Again, it has a discharge date due to illness/injury.
My understanding is that injured men were returned to reserve battalions pending treatment/discharge.
Interestingly a medal index card and 1915 star/War and Victory medal rolls entries exist for an Archibald McDonald, Cameron Highlanders, with the same service number. Theatre of war is confirmed as France on 10/5/15.
Also interestingly, he is also recorded as having service with the 5th Battalion CH.
Hope this helps,
David
Quick check with 1914-1918 net
5th (Service) Battalion
Formed at Inverness in August 1914 as part of K1 and came under orders of 26th Brigade in 9th (Scottish) Division.
Moved to Aldershot and in February 1915 went to Bordon.
Landed at Boulogne on 10 May 1915.
http://www.1914-1918.net/9div.htm