The Neutrality Game I

There is evidence that Portugal had an illegal wolfram commerce during WWII. The metal that's crucial to the German Tanks build. In the year 2000, more than a thousand documents were uncovered in an old abandoned Spanish railway station, showing 75 tons of nazi gold had passed through the border on its way to Portugal. Which brings us to a sensible question: to whom did the responsibility fall to confirm the Nazi gold's legitimacy?