Perhaps his father spent some time in Canada? The mismatches between cases and scopes presumably occurred over time in service. We now have five or six scopes showing up in the UK in contrast to the two sent for appraisal in 1945. But over time rifle teams travelling back and forth etc. could account for that. The kit was sure to appeal to marksmen for range use, and might even have been issued to Canadian service rifle teams? Presumably they were surplussed off sometime around the introduction of the FN C1A1.