>>2079
I've seen it referenced in early 1900s publications. I think the bigger concern isn't stocking two ammunition, it's being able to find replacement ammo in the future to avoid having a useless gun, so picking something that's absurdly common for both minimizes the issue. Even in the interwar, American hunting publications were suggesting 44-40 as round for foreign hunting trips on the explicit rationale you'd actually be able to find ammo virtually anywhere in the world. Imagine trying to find something like .44 Colt in a country that barely has civilian handguns.