"The price for ridding society of bad is always high. Love, Daddy."

The handwritten letter, sent by future CIA Director Richard Helms to his 3-year-old son at the close of World War II, may not be as ominous as bin Laden’s AK-47 featured in this exclusive NBC News report, which rests in another of the private museum’s display cases. But it too serves as both a trophy of war and a reminder of evil.

“Dear Dennis,” reads the letter from Helms, then a spy stationed in Germany. “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. He had a thirst for power, a low opinion of man as an individual, and a fear of intellectual honesty. He was a force for evil in the world. His passing, his defeat – a boon for mankind. But thousands died that it might be so. The price for ridding society of bad is always high. Love, Daddy.”

The letter was among a trove of memorabilia that Dennis sent to the museum 66 years later, in May 2011, to form part of an exhibit that pays tribute to the CIA’s roots in a wartime agency called the Office of Strategic Services, or the OSS.