Sentence:  The gruesome humor of the Nazis was not forgotten - the gas chamber with a sign on it with the name of a Jewish foundation and bearing a <WSD>copper</WSD> Star of David - nor the gratuitous sadism of SS officers . 
Meaning of the word marked with <WSD> tags:  a ductile malleable reddish-brown corrosion-resistant diamagnetic metallic element; occurs in various minerals but is the only metal that occurs abundantly in large masses; used as an electrical and thermal conductor