Hi:
In reference to your question, "Could WWII Vets bring back Machine Guns As War Trophies" ?
I was a small lad during and after WWII. My Father's Friends did and wherether it was legal or not ??
I remember not only rifles, pistols, knifes, and swords but SMGs, MGs, grenades, artillery shells, helmets, etc.
My first Agency (1962) had a German MP-38 9mm that a WWII Vet had given to the Agency. He also brought back a huge German Flag and a duffel bag full of Lugers.
The last time I looked in one of Dad's Friend's foot locker there was still a live Jap Hand Grenade !
Two years ago one of my Officers during a traffic stop found a Jap Nambu MG in the trunk of the stopped car. The two young ladies had found the MG in their Grandfather's attic and was taking it to trade for drugs.