King Charles Debuts New Royal Cypher, Which Will Gradually Replace Queen Elizabeth's

King Charles III has a new emblem.

The King's new royal cypher has been revealed by Buckingham Palace as Charles begins his third full week as head of state.

The monogram shows the crown above his first initial "C" intertwined with an "R" for Rex (Latin for King, traditionally used for the monarch dating back to the 12th century), with "III" inside the "R."

It will soon become commonplace where royal symbols are shown, replacing Queen Elizabeth's "ERII" insignia. Some of these changes will be gradual, palace officials say, but the postmarks on all mail leaving Buckingham Palace will begin on Tuesday. The cypher will also be seen on state documents and eventually on the familiar red mailboxes around the U.K. as well as used by U.K. government departments on their mail.

The new cypher is the personal property of Charles, 73, who officially ended the period of royal mourning for Queen Elizabeth on Monday along with other members of the royal family and the royal household. He chose the design from several that were created by the palace's heraldry experts, the College of Arms.

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Buckingham Palace/PA Wire

The King already adapted a new signature that came with his place as sovereign, signing his name as "Charles R" on official documents as well as the note left on top of Queen Elizabeth's coffin during her funeral services.

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During her historic reign, Queen Elizabeth would sign official communications as "Elizabeth R." When used by Queens, the "R" stands for "Regina," or "Queen" in Latin.

Max Mumby/Indigo/Getty Images; Buckingham Palace/PA Wire King Charles

The King, who is currently staying in Scotland, also has a slightly different version for use in Scotland — that cypher features a depiction of the Scottish Crown. King Charles and Queen Camilla's time in the highlands of Scotland followed an intensely busy period of public events and ceremonies, which King Charles had to carry out amid his own mourning at his mother's September 8 death. She died "peacefully" at Balmoral Castle at age 96.

Buckingham Palace/PA Wire

On Sunday, King Charles and Queen Camilla headed to Crathie Kirk near Balmoral for church services as they continue their stay in Scotland.

Last week, the King's office released a photo showing him at a mahogany desk in Buckingham Palace's Eighteenth Century room, working through the papers that are delivered to him every day in the diplomats' red boxes.

Victoria Jones - Pool/Getty King Charles

Behind Charles is a black and white photograph of his late parents, Queen Elizabeth and Prince Philip. It was given by the couple to her father, King George VI, for Christmas in 1951 — the last holiday season before he died in February 1952.

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NIALL CARSON/POOL/AFP via Getty King Charles and Queen Camilla

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As he adjusts to his new role as monarch, Charles' character has been on display, but he has largely come through it with the backing of the British people, a biographer told PEOPLE.

"It's been interesting because he's been clearly buoyed and moved by the public support for him," says Catherine Mayer, whose book Charles: The Heart of a King has been recently updated. "I know him well enough to know he'd be surprised by that. He always expects to be the one who disappoints. But the excitement has lifted him."