Kupers, now 83, played with Frank in Amsterdam before Frank and her family went into hiding in a concealed "Annexe." Space was limited, so Frank asked Kuypers to keep watch over her toys.
"She immediately contacted us," da Silva said of Kupers' discovery. "We were thrilled that the marbles survived and had been kept. She decided to give everything to the Anne Frank House -- the book, the tea set and the marbles."
The book and the tea set have already gone on display at the Anne Frank House, but the marbles first appeared at the The Second World War in 100 Objects exhibition in Rotterdam on Tuesday.
Kupers family also took care of the Frank family cat, Moortje, mentioned by Frank in her diary.