The rifle appears to be a standard Mark II** Snider-Enfield Rifle - i.e. "long rifle", with three barrel
bands and brass furniture (nosecap, triggerguard and buttplate) issued primarily to Infantry units.
(The other most commonly encountered type of Snider-Enfield with Canadian markings is the "Short
Rifle" - barrel 6" shorter, only two barrel bands and the "furniture" is iron rather than brass -
issued primarily to Sergeants of Infantry and to all Other Ranks in "Rifles" units.)
As already noted the "D C" is a Canadian government ownership mark - denoting "Dominion of
Canada" - adopted very shortly after Confederation, and in use throughout most of the rest of
the 19th Century (along with some other less common marks like "CM" (Canadian Militia)
and "MD" or "M&D" (Department of Militia and Defence.)\
Regulations called for the DC mark to be stamped on the wooden buttstock (left side) and
technically the letters should be within a diamond shaped border - though some units
apparently didn't have the special stamps issued for that purpose, or misinterpreted the
instructions, or whatever, since it is not uncommon to see the mark without the diamond,
like yours, and also elsewhere on the stock - most commonly on the right side of the butt.
(A copy of the original marking instructions is appended at the end of the post.)
The DC initials will be seen both with and without periods - here are examples of both -
note that the second one involved a rifle being re-marked at some time in its military career -
The G V A mark has been noted on other rifles - at least one of which is documented in
an appendix to David W. Edgecombe's
"Defending the Dominion: Canadian Military Rifles,
1855-1955", though no specific meaning is ascribed to it, and I was in contact with
another fellow a year or so ago who had a rifle with the same mark. One guess is that it
stands for "Garrison Volunteer Artillery", or something like that - Canada's military forces of
the day were all volunteer militia, with different types of units, including "Cavalry",
"Infantry", "Rifles", ""Field Artillery" (i.e. manning field guns) and "Garrison Artillery" (manning
guns in fortifications.) However, militating against that interpretation is the fact that yours
is a "Long Rifle" (as is the one documented in Edgecombe's book - I can't recall offhand
which version the other one was) - whereas Artillery units were generally issued the Short
Rifle. So who knows ...
Anyway, here are the original marking instructions: