Well you've taught me something today, Thank you.
I've heard that the British government converted many .455s to .45acp for logistics and I've also heard importers modified them for the surplus American market. I like to think it served the allies in both world wars but I have no idea if thats true or false.
Its got English proof marks, it was over there. Like many men who served, being there was service.
But not with those grips.