Queen Elizabeth II’s coffin, which will rest in London for four days later this week before her funeral next Monday, was reportedly crafted more than three decades ago.

The coffin will rest closed on a raised platform known as a catafalque in Westminster Hall – the oldest part of the centuries-old parliamentary estate – from Wednesday after resting in Edinburgh for a day from later Monday.

Here are more details about the coffin of Britain’s longest-serving monarch:

The Queen’s coffin was made from English oak at least 32 years ago, which is becoming increasingly rare these days as most wooden caskets are now made from American oak, the Times reported on Monday.

It is lined with lead, a royal tradition to preserve the body longer after its burial in a crypt – on this occasion at the King George VI Memorial Chapel at St George’s Chapel in Windsor, west of London.

Lead is said to make the coffin airtight, which helps prevent moisture from entering, but makes it considerably heavier. The Queen’s coffin requires eight pallbearers to move.

It matches another made for the late Queen’s husband, Prince Philip, who died last year and was buried in the crypt, where she will soon be buried alongside him.

Leverton & Sons, London undertakers for the royal family since 1991, told The Times they inherited the coffins at the time and were unaware of who previously made them.

“It’s made from English oak, which is very hard to come by,” Andrew Leverton, who runs the company, added to the newspaper.

“I don’t think we could use American oak for a coffin now. That would be too expensive.”

The coffin was specially designed to hold valuable belongings securely on its lid.

In the case of burial and burial, these include the imperial state crown, orb and scepter, which represent various aspects of the sovereign’s power.

The brass handles on the coffin are also uniquely designed for royal caskets, which are made by a company in the central English city of Birmingham, according to The Times.

“It’s not something you can do in a day,” noted Leverton.

Queen Elizabeth II’s coffin first emerged on Sunday, covered with the Scottish Royal Standard and a wreath of white heather, dahlias and sweet peas, from the gardens of the Balmoral estate, where she died on Thursday.

It rested overnight at the Palace of Holyroodhouse in the Scottish capital, Edinburgh, on Sunday.

On Monday it rides with a hearse – followed by a procession with King Charles III. and other high-ranking royals – to St Giles’ Cathedral on the Royal Mile, where it will remain 24 hours.

It will then travel to London on a Royal Air Force plane, where it will sit at Buckingham Palace before moving to Westminster Hall on Wednesday.