"We believe it was brought back to England by my grandfather who was stationed in the Far East during the Second World War and was awarded a Burma Star," the seller said.
The man said the item was nearly donated to a thrift store, but he decided to have it appraised and was surprised to learn it was an 18th century Chinese wine ewer that may have been used in the palace of Emperor Qianlong.
Hansons said there are two "nearly identical" items known to exist and they are housed at museums in China and Taiwan.
The ewer had been expected to sell for up to $50,000, but ended up fetching a high bid of $495,880.32 at Thursday's action.
"I'm thrilled, this will change a few things for us all. I sat and watched the auction live at home with my brother and family," the seller said after the auction. "It was tense. I got a few cans of Guinness in beforehand. We'll be going for a drink tonight and toasting granddad."
Auctioneer Charles Hanson said the price was driven up by a bidding war between eight participants from around the world before the final bid was placed by the London buyer.
"This is one of the most important objects I've ever had the privilege of selling. It has to be the best lockdown find ever," Hanson said.