Until the early 20th Century, Canada had no Army or Navy (and Air Forces were a thing of the future, of course.) Instead, our military was made up entirely of Militia - i.e. volunteer, part time soldiers. In the late 19th Century Parliament finally created a "Permanent Militia" (full time, professional soldiers, who acted as a training cadre for the rest of the Militia) but its total strength was limited to 750 men! (Later raised to 1000.)
Military affairs were administered by the Department of
Militia &
Defence - which was the full name of the "Militia Department" mentioned in the Note quoted in my posting. The "M&D" stamp you refer to was the "government acceptance & ownership" mark used before adoption of the C-broadarrow. The main such mark
prior to "M&D" had been "DC" - signifying Dominion of Canada - usually enclosed within a diamond shaped border (used in and after 1867) .... and before Confederation military firearms and such owned by Canada (then consisting of just Upper Canada and Lower Canada) was "CM", standing for "Canada Militia" ...
Now, does what you are describing as "opposed spearheads" look something like this? -
If that is what the mark looks like (sometimes the points will be touching, sometimes slightly separated) then it is actually "opposed
broadarrows" - a "sold out of service" mark, signifying that the firearm had been "surplused" and disposed of legally. (The traditional British government ownership mark applied to firearms and such was the "Broadarrow" - when such items were "sold out of service", that mark was "cancelled" by striking another arrow opposing the first (or even applying a separate "opposed arrows" mark.) Even though Canada had not yet adopted its own distinctive broadarrow mark, the British version may have been used - or at least the "opposed arrows" mark when disposed of. For that matter, the rifle could have ended up in British service (I believe many were sent there during WWII for Home Guard use) before finally being surplused.
The other numbers you mention are likely "issue" or "rack" numbers ... The traditional method of "unit marking" rifles which had been issued was to mark them with a regimental or battalion number (or letter abbreviation) plus a "rack number". For example, if 500 rifles were issued to the 55th Battalion, they would all be numbered "55", and also further numbered from 1 (or 001) through 500. However, if I am not mistaken, during part of the period the Ross rifle was our official military longarm, it may have been the practice to mark the rifle with the regimenatl number (i.e. serial number) of the individual soldier it was issued to - that could well be what the longer number is ... Matter of fact, Ross rifle butts (more so than any other Canadian military rifle) are often marked with an absolute proliferation of such stamps, one set being struck out and another set added, and so on ...