Biden gives Pope a sentimental challenge coin: 'The next time I see you, if you don't have it you have to buy the drinks'

In video footage provided by Vatican Television, the two men were seen exchanging a number of gifts, including what's called a challenge coin -- historically collectable pieces of recognition that originated in the military.

Biden said the coin he handed Francis included insignia of the 261st Signal Brigade unit in the Delaware Army National Guard, the unit in which the President's son, Beau Biden, served as a captain.

"With your permission I'd like to be able to give you a coin. It has a US seal on the front, but what's different with this coin, usually -- I know my son would want me to give this to you because on the back of it I have the state of Delaware and the 261st unit my son served on," Biden said, handing the Pope the large gold coin.

Beau Biden died in 2015 at the age of 46 from brain cancer. The President saw the Pope in the following months, and has warmly recalled when Francis gathered with Biden's extended family, who were still grieving, as he departed from the Philadelphia International Airport on his way out of the US. Biden has also said he corresponded with the Pope following Beau's death.

The President said during Friday's Vatican visit that the coins are given to "warriors and leaders," adding, "You are the most significant warrior for peace I've ever met."

"Now the tradition is -- I'm only kidding about this -- the next time I see you, if you don't have it you have to buy the drinks. I'm the only Irishman you've ever met whose never had a drink," Biden said to the Pope, who was laughing.

Francis quipped that "Irish people love whiskey."

The President also gave Francis a hand-woven vestment from the 1930s that came from Biden's Washington, DC, parish, Holy Trinity Church.

The Jesuit church, established in the late 1700s, was also attended by President John F. Kennedy.

The Pope's gifts to the President included a ceramic tile with an etched design, as well as his recent writings.

Later, Biden -- aged 78 -- joked about age with Francis, who is 84. Relaying a story about the African American baseball player Satchel Paige, Biden described his attitude toward aging: "How old would you be if you didn't know how old you were?"

"You're 65," the President said. "I'm 60. God love you."

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