The King was given a replica of a President Eisenhower Sword by Donald Trump and first lady Melania Trump during the US leader's state visit to Britain.
The gift was described by Buckingham Palace officials as a symbol of the"historical partnership that was critical to winning World War Two".
They said the sword also"symbolises the enduring values and cooperative spirit that continues to define the relationship between the United States and Great Britain".
Dwight D Eisenhower was Supreme Commander of the Allied Expeditionary Force in Europe during WWII, presiding over D-Day, and later became the 34th president of the US, serving from 1953 to 1961.
The Queen was gifted a Tiffany & Co vintage 18-carat gold, diamond and ruby flower brooch.
'So beautiful'
It comes as the president appeared to tell the Princess of Wales she was"so beautiful" as he and Mrs Trump were welcomed by the Prince of Wales and Kate to Windsor Castle.
Mr Trump was first greeted by William with a handshake, and the president, who was affectionately patting the prince's right arm, appeared to say:"Hello, my friend. How are you?".
Kate, dressed in a burgundy Emilia Wickstead dress, a matching hat by Jane Taylor and wearing a feather brooch, was next to welcome the president.
Mr Trump moved on to shake the princess's hand, and she gave him a broad smile as he appeared to tell her:"You're so beautiful, so beautiful."
'This is my father'
The Trumps and the Waleses then approached the King , as William told Mr Trump,"This is my father", before the president shook the monarch's hand and placed his hand on his arm.
Also, the King shared an exchange with the president as they walked along the line of honour guard at Windsor Castle.
'Watch the sword'
Pausing at the end of the row for a moment, they look upon one trooper holding a ceremonial blade.
"Watch the sword," the King appeared to say, nudging the US leader and smiling.
They then watched as the soldier twirled the weapon expertly, with Mr Trump appearing to say a few words with the sword bearer.
What did the royals give the Trumps?
The palace added that the King and Camilla have given their American guests presents at Windsor Castle.
The royal couple gave the president a bespoke, hand-bound leather book specially crafted by the Royal Bindery in Windsor Castle to celebrate the 250th anniversary of the Declaration of Independence, which was adopted in Philadelphia on 4 July 1776.
They also gifted Mr Trump the Union flag that was hoisted above Buckingham Palace on the day of the president's inauguration on 20 January this year.
To Mrs Trump, the King and Camilla gave a silver and enamel bowl featuring the Queen's cypher crafted by Northern Irish artist Cara Murphy, a top silversmith who has created works for Downing Street and the Grand National.
The first lady also received a personalised Anya Hindmarch handbag.
