Thanks to Darcy Murray, who posted a comment on my original post about Captain Slatter, I learned that this is the dress uniform of the 48th Highlanders of Canada. This morning, Lt. Kassissia of the 48th Highlanders responded to my inquiry by confirming that yes, Captain Slatter does appear to be wearing the 48th Highlanders' uniform and my inquiry will be forwarded to the Regimental Museum for further study!
In Canada, November 11 is Remembrance Day, as in America it's Veteran's Day. So this week I want to post a poppy in remembrance of Captain Slatter and all those veterans who have served our nations. Thank you for your service!