The cistern, as big as a small bath, was commissioned by the third Lord Raby after being appointed Ambassador Extraordinary to Berlin in 1706.
Queen Anne gave each of her ambassadors a quantity of silver to furnish their embassies, impress their guests and show the wealth of the nation.
Lord Raby decided to pour more than half his 5,893 ounces of silver into this one cooler, designed by Philip Rollos, one of London’s finest goldsmiths.
Mario Tavella, deputy chairman of Sotheby’s Europe, said: “It’s a huge status symbol, a huge trophy.”
The cooler, which weighs 11.5 stone, is estimated to sell for between £1.5 million and £2 million.