At CIA headquarters in Langley, one of the newest artifacts in the agency’s private museum is a message from a father to his 3-year-old son. The gold-embossed letterhead features a swastika and the name Adolf Hitler.

“Dear Dennis,” the seven-sentence letter begins. “The man who might have written on this card once controlled Europe — three short years ago when you were born. Today he is dead, his memory despised, his country in ruins.”