Found an interesting comment on YouTube while looking for versions of the song.

"Bill McRobb
1 month ago
The song is about Sergeant McGaw of the Black Watch, 42nd Highlanders, who won the VC in the Ashanti War of 1874 during the Gold Coast campaign (now Ghana) the medals have Coomassie on them."

From https://www.youtube.com/watch?v=UaWExv0KQ74