I don't believe that the NWMP received any Martin-Henry carbines. 10 were ordered in 1874 for test purposes but a delay in approving the weapon, or specifically the ammunition, put off their availability until 1877. What was issued to the force in 1874 were 10 M-H rifles. They were not adopted for service, and only one per troop were issued. As far as I can see they were only of any use in shooting matches with the Militia.
What is interesting is that in 1874, due to the poor condition of the stock of Adams revolvers, 30 S&W "Old Model Russian" revolvers were purchased in Fort Benton and issued to recruits. One officer, Sub-Inspector Allen, owned a private purchase S&W OM Russian as well. This is the only NWMP revolver that is available as a newly made reproduction.