In 1885, due to the impending North West (Riel) Rebellion, the Government of Canada ordered 1,001 Colt Model 1878 Double Action revolvers in .45 Colt ('Long Colt') calibre. Some of these may have been carried by members of the NWMP, others issued to members of the Canadian Militia for use in the North West Campaign.
The first Canadian contingent sent to South Africa (Boer War) were issued these Colt 1878's. This contingent was made up of a formation from the Royal Canadian Regiment (RCR) and the Canadian Mounted Rifles (CMR).
These revolvers were stamped with "MD" (Militia and Defence) numbers.
I acquired one of them a few months ago and have since sold it to another CGN who collects Colt revolvers.
The second contingent sent to South Africa carried the Colt 'New Service' revolver.