Eng Charles was photographed with his red box for the first time.
The image, taken last week, shows the king carrying out official state duties in the eighteenth-century room at Buckingham Palace.
The red boxes contain the papers of British and royal government ministers as well Commonwealth of Nations representatives.
The documents are sent from the private secretary’s office to the King, wherever he is around the world, in a locked red box.
These include papers that require a signature, informational documents and information about upcoming meetings.
In the picture, Charles is sitting at the table. There are papers nearby, one tied with a ribbon.
Also shown is a black and white photograph of the late Queen and the Duke of Edinburgh, given by the couple to King George VI for Christmas in 1951.
Earlier, luxury British leather company Barrow Hepburn & Gale confirmed that boxes for Charles are being produced.
On September 11, a representative of the firm said that the king would initially receive more than six boxes of the new royal cipher.
It is possible that 10-12 boxes will be produced and delivered in stages over the coming months.
Each box, the price of which is never revealed, has its own code lock and is designed to last for many years.
On its website, the company says its boxes “follow their owners around the world, ensuring they can fulfill their office duties.”
It adds: “Wherever the sovereign or minister is in the world, the red box is nearby.
“Our shipping boxes are not only elegant in design, they are functional and safe.”
In September 2015, the royal family’s Facebook account said the Queen received red boxes every day of her reign, including weekends, but not Christmas.
The report said the Queen still uses boxes made for her coronation in 1953, which have been “repaired periodically” to keep them in good condition.
Barrow Hepburn & Gale said the role of boxes “has not changed for over a century”.
It adds: “There are two possible reasons why the box became the famous red colour.
“The widely recognized reason is linked to Prince Albert, consort of Queen Victoria, who is said to have preferred this color as it was used in the arms of his family, Saxe-Coburg-Gotha.
“However, there is a school of thought that dates back to the late 16th century, when Queen Elizabeth I’s representative, Francis Throckmorton, presented the Spanish ambassador, Bernardino de Mendos, with a custom-built red briefcase filled with black puddings.
“This was seen as an official message from the Queen and so red became the official state colour.”