A new collection of collectible American coins by British designer Harry Potter has sold at auction for $4 million.

The collectible silver penny commemorates the first American war, which ended in 1865 with the signing of the Treaty of Versailles.

The coin, which is the most expensive piece of American silver ever sold, is set to be auctioned in a private sale to raise money for a new Harry Potter museum in England.

“We are delighted to be able to share this new Harry Potter collectible with the world and look forward to a new generation of collectors and collectors of all ages watching in awe as this coin reflects the spirit of the Harry Potter universe,” the British-based company said in a statement.

It was the second-most expensive collectible in history and the second most expensive in British history, the auction house said.

The auction house had hoped to sell the coin in a bid to raise funds for the Harry Potters’ new HarryPotter.com website, which has become the most visited site on the internet for the Potter franchise.

The Potter universe is a global phenomenon, with Harry Potter, his family and friends from around the world visiting London to visit Hogwarts, which celebrates its centenary in 2019.