We return once again to the tumultuous events of the Second World War, but this week our quest for answers to questions nobody asked heads for Europe. Ready?

Copenhagen, April 1940. Germany invades Denmark. The chemist George de Hevesy had some time prior been given two articles for safekeeping by his German friends Max von Laue and James Franck. Hevesy knew there would be serious consequences if they eventually fell into Nazi hands. As the German forces marched in the city, de Hevesy dissolved each in a powerful solution of aqua regia. When the Germans searched his lab, they saw nothing noteworthy in the containers of the acrid solution, which remained undisturbed through the war. After the war was over, Hevesy extracted the dissolved material from the solutions.

What were the dangerous possessions with which Hevesy was concerned?

First correct answer posted to comments wins a tattered copy of the sole issue of the 1943 comic THE MALINGERER (in which PFC Gordon Crimp, aka THE MALINGERER, simulates a case of food poisoning in order to smoke out an Axis plant in the chow line at Allied Command). No Googling or instant-messaging Tom Brokaw. One guess per comment, please, but you may comment as often as you like.