LOS ANGELES (Reuters) - A one of a kind 18th century gold coin bearing the likeness of the first U.S. President, George Washington, is expected to fetch more than $1 million when it goes up for auction in August, auctioneers said on Wednesday.

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The 1792 Washington President gold eagle coin was never circulated as money, but is instead thought to have been presented to Washington when post Revolutionary War plans were being drawn up for the first U.S. Mint.

Washington refused to have himself depicted on coins, considering the notion “monarchical.”

Currency researchers believe that the Washington President coin, which has his head on the front and an eagle on the back, was given to him as part of a sales promotion in a bid to obtain a contract to strike U.S coinage, and that Washington carried it as a personal memento.

The U.S. Mint was authorized in 1792 and the first coins for public use were issued a year later in copper and silver, with images of lady Liberty on the front and a bald eagle on the back.

The Aug. 16 auction during the World’s Fair of Money convention in Philadelphia marks the first time the Washington President coin has come to public sale in 128 years, Heritage Auctions said in a statement.

Jim Halperin, co-founder of Heritage Auctions, said the coin was “unique and monumentally important, being the earliest gold pattern submitted for consideration as a United States coin.”

“Numismatic researchers widely agree that it is almost certainly George Washington’s own pocket piece,” Halperin said.

Heritage Auctions said the $1 million is a starting estimate because the coin is a one of a kind piece.

Prices for Colonial era coins, which set the standard for the modern American banking system, have soared in recent years because of their scarcity and the desire to own a piece of history.

The Washington President coin comes from the collection of the late Eric. P. Newman, who acquired it privately in 1942.

Newman died in 2017 having amassed one of the most significant coin collections in the United States. Thousands of lots have been sold in recent years with net proceeds benefiting Newman’s museum operation, numismatic research and other charities supported by him.

The Washington President coin will be publicly unveiled at the Coin and Collectibles Expo in Long Beach, California on Thursday, and will be displayed in New York and Chicago before the Philadelphia auction. All the proceeds will go to Newman’s non-profit causes.