On September 26 2017 I received this P56 carbine in a trade. (.577 cal.)
The lock plate has Crown over VR and 1861 over Tower.
(Different from the P.53 Enfield rifled musket shown above with no 'VR' under the Crown)
The Confederacy purchased 10,000 of this model carbine-----this was not one of them.
Comments from a fellow who is much more knowledgeable than I am.
The “1” under the stock roundel actually means that, following completion, the carbine was rated as a “First Class Arm" - although the result of that would generally mean that it would be most likely to be issued to a regular unit in the British Army , it would not preclude loan and/or sale to one of the self governing colonies, such as the various colonies in British North America , the various Australian colonies, etc. (A “Second Class” arm would be kept in reserve, or perhaps be issued to British militia, or perhaps colonial forces. The fact that the lockplate does bear a complete Royal Cypher (the crown over V.R.), the stock roundel is the official War Office Tower Armoury mark, and the various other broad arrow marks would confirm that this was indeed a carbine made under contract for the British Government, albeit with those markings it was clearly not made at Royal Small Arms Manufactory Enfield, but rather was produced by one of the independent contractors who also made such arms for the government - and who also were allowed to make other arms for private sale or export - e.g. to both the United and Confederated States during the ACW.
Although it is apparent that Canada did not purchase any P’56 cavalry carbines in its own right, a number of such carbines were loaned from Imperial Stores, apparently as early as 1858. As nearly as I can make out from my references, there were at least 500 such carbines on loan, but perhaps as many as 1,000 or possibly even more. The Militia forces in British North America were significantly bolstered following the Trent Affair in 1861. and a mid-1862 report refers to a request for 500 cavalry carbines from Imperial Stores; also. a written application for loan of arms in November of that year refers to 1,000 cavalry carbines (although it is unclear whether this number includes - or is in addition to - the 500 previously mentioned.) At any rate, it seems apparent that the cavalry strength had been increased, or it was anticipated there would be such an increase.