When Canada started producing their own 37 pattern webbing in the Second World War, they modified the British design of skeleton water bottle carrier in 1942 to closely resemble that introduced by Mills in the earlier 1919 pattern set. What this meant in reality was that the water bottle had a single long fastening strap, secured to the rear:This passed over the top of the bottle and fastened to a press stud on the front of the carrier:This was in contrast to water bottle carriers from other countries of the Empire where the fastener was on the top shoulder of the bottle. At first glance the 1919 and Canadian 1937 pattern water bottle carriers are identical, however we can tell them apart either by the markings (which are very hard to make out on this example) or by the press studs themselves. These are made by United Carr of Canada:As to why the Canadians changed the design of the carrier; that is a harder question to answer, presumably it was felt that by moving the fastener to the front manufacture could be speeded up as you were not having to sew two straps to the rest of the carrier. It also reduced the amount of brass needed as you were only reinforcing on strap end with a brass chape. It might also have made it easier to open and close the carrier when worn as the strap would be easier to access on the front of the carrier than it would on the top. There are a lot of weird and wonderful changes made by Canada to their webbing over the war years, resin impregnated tips and unique construction techniques amongst others. For those with an interest in the subject I cannot do better than point you to this thread here on Canadian webbing which is excellent.