I'm a little late finding this thread, but here goes .....
First, here is my .450 Adams "Model of 1872" - (click thumbnail images to enlarge ....)

This example is
not NWMP-issue ... but then I got it for a
lot less than I'd have had to pay for Mounted Police revolver.
The "Mark III" (M'1872) Adams was the model the NWMP were expecting to receive right from the outset - the order to the War Department, placed in late 1873 or early 1874, having specified the "latest model" of British service revolver. The revolvers still hadn't arrived when the NWMP were otherwise ready to start off from Dufferin, Manitoba, on the "Great March West" in 1874, and their departure was delayed until the shipment arrived. When the crate was opened, they were astounded to discover that what had been sent were "First Model" Adams cartridge revolvers - which were in fact conversions from percussion ignition to cartridge revolvers (and thus only 5-shot rather than 6-shot) and also that the "trade contractor" to which the War Department had apparently "farmed out" the order had simply placed all the revolvers together in the crate - without separation or proper packing - with the result that many of the pieces were damaged. A further delay ensued, while the NWMP armourers repaired what they could (cannibalizing parts from some of them) and the Force then set off on its trek without a full complement of handguns.
A complaint through official channels resulted in this first shipment of revolvers being replaced with Mark III Adams revolvers - in 1875, IIRC.
The NWMP adopted the .476 Enfield revolver in 1882, when it was already coming under criticism as awkward and somewhat unreliable in its role as the then-current British service revolver (resulting in its replacement by the Mark I Webley revolver in 1887) .... and it was retained as the primary Mounted Police handgun until 1905. Here is my example, which
is recorded as being NWMP-issue:
By the way, the common assumption that Canadian police and military handguns have been British models is erroneous - The RCMP have used American models since adopting the Colt New Service revolver in 1905, and Canadian military forces have
never adopted what could be considered a primary-issue handgun that was British! For more information, check out this online article I was privileged to author - illustrating it mostly with handguns and holsters from my own collection ....
http://www.canadiansoldiers.com/weapons/pistols.htm
(I see that some of the image links in the article appear to be broken, and I'll fire off a message to the webmaster of that site about it.)