The painting is believed to have been plundered by high-ranking Nazi Hermann Goering during World War Two.
The commemorative stolpersteine stones provide individual memorials for those who experienced occupation.
He was saved by a Jersey family after escaping a Nazi labour camp, but after the war he disappeared in the Soviet Union.
Peter Martel recalls his memories of a "hard period" for Guernsey.
On the 85th anniversary of the Blitz and ahead of a new play about it, BBC News NI talks to 93-year-old Reggie who lived through it.
Christian Rainer told the BBC he found his grandfather within seconds using the online tool, which also helped clear other members of his family.
The story behind Operation Mincemeat, a wartime deception plan to fool Hitler and the German forces.
Max Wenner was rumoured to have links with prominent Nazis and died after taking a flight in 1937.
The billionaire says "anti-semitism is always in the air".
