Production of the General Service Respirator began in Canada before the outbreak of the Second World War. Canada had the manufacturing capacity and infrastructure to produce this complicated respirator and the finished products are very similar to British made examples, but with Canadian property marks and the names of Canadian manufacturers stamped into them. The respirator was, of course, only part of the anti-gas system and Canada also produced anti gas clothing, ointment, brassards and the subject of today’s post the haversacks to carry all of these items. Originally Canada would have produced the same Mk V design as Britian but by 1940 this had been updated to the Mk VII and it is a Canadian produced Mk VII haversack we are considering today:

At first glance, apart from being a lighter shade of cotton, the haversack does not look much different to the standard British made example. Up close however we can see a number of small changes. The most obvious is in the interior where the loop at the base for the anti-dimming outfit has been replaced with a small interior pocket secured with a press stud:

Also different is the arrangement for the whip cord that goes around the back of the wearer when the haversack is in the alert poition. The cord itself passes through a blackened eyelet and has a small pocket in which is it kept on one side of the haversack:

On the opposite side, instead of the brass D-ring of the British Mk V or the pressed metal disc of the Mk VII we have a cord loop, again passing through an eyelet:

Internally, apart from the pocket, the layout is the same as the British haversack (although the cross divider has been removed form this example at some point in its life):

The base of the haversack has a single brass intake vent to allow air to be drawn into the canister of the respirator when it is being used:
Under the top flap, alongside an inked post war civilian address, can be seen the /|\ within a ‘C’ ink stamp showing that this haversack is Canadian Army property:

These respirator haversacks are distinctive and were designed for issue to Canadian troops, however the differences are subtle and once in the UK it is very likely that Canadian troops would have been issued from pool stock produced in the UK. Equally much Canadian made equipment such as this haversack was exported around the world including to places such as Italy and Australia so the haversacks would have ended up scattered across the Empire.
I ownone of these. I used it for years as my archery range bag.