A stamp issued in 2006, featuring Maurice Sendak's "Wild Thing" as part of the USPS's "Children's Book Animals" series.

The first day of issue cover for a 2006 stamp featuring Maurice Sendak's "Wild Thing" as part of the USPS's "Children's Book Animals" series.

A card from a 1967 Holocaust remembrance rally in Israel, featuring Korczak and his children.

Hyannis, Massachusetts. This part of the country has never been known to be all that friendly to Jewish people. Mrs. Wagoner’s boarding house for “Restricted Clientele” was no different.

An original, handwritten, six-page letter from Irena Sendler — with its original envelope. The letter was authenticated by Holocaust experts and then translated by my friend Mieczyslaw.

The key players in the Dreyfus Affair, featured on this never-mailed 1898 French postcard.

This first-day-of-issue cover for France’s 2006 stamp commemorating Alfred Dreyfus features the officer rightfully declaring his innocence during his sentencing.