The stories about hidden German army weapons and munitions were certainly circulating when I was there in the mid-1960s in the army.
As you all probably know, Mosin-Nagant rifles were manufactured in the United States for the Russian government, only most were not delivered because of the revolution. Some of those ended up in the hands of the militia, if what I read is true.
Concerning underground munitions, there used to be frequent news stories about munitions from WWI turning up during construction in Washington, DC.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.