Haven't seen those Browning boxes before either - very cool find.
The Imperial one I have in the 5 pack. Pretty neat part of history.
It is interesting where some of these come from. I had a guy who sold me an absolutely ancient Canuck box of shotshells (think it had only 9 or so out of the original 20 or 25) - the box looked like it was from the 1940s or so - waterproof paper hulls or something. The guy was about my vintage (middle aged) so I asked whether he inherited it from family members. He said no, he had an old neighbour who passed away. His wife, also old, was cleaning out their garage (sounded like a hoarder's paradise) and found out he had not only ammo, but long guns (rifles/shotguns). She apparently had no clue, which was interesting given they were married for over 60 years... Anyways, she didn't know what to do with it all so she took all the ammo in an orange crate and dumped it on their neighbour's porch (not sure if she knew he was a gun owner or not, thankfully he was). He does not shoot shotguns at all and so offered a bunch of this stuff to me at a bargooon price. I never plan to shoot this vintage ammo, but have it on display just for a part of Canadian history