NEW YORK — A rare 1907 double eagle $20 coin designed by Augustus Saint-Gaudens could sell for as much as $1.5 million at auction next week.

The lustrous gold piece is one of four experimental relief $20 coins that were minted in Philadelphia in 1907 between Feb. 7 and Feb. 14. A majestic flying eagle appears on one side and a figure of Liberty on the other. The coin is one of only two with sans serif-edge lettering.

President Theodore Roosevelt commissioned noted American sculptor to redesign the $20 gold piece. Saint-Gaudens died a few months after the first Ultra High Reliefs were coined.

Paul Song, director of Bonhams’ department of coins and banknotes, said he discovered the coin in 1992 at an estate and it was sold at auction for $143,000.

Bonhams is offering the coin for sale Tuesday on behalf of an anonymous American collector. It is estimated to bring from $1.25 million to $1.5 million.

“This is the only one that will be available to collectors in the near future,” said Song.

The second existing sans serif coin sold at auction in 1995 to a private collector for $242,000.

Song said the two coins “are the only ones that Saint-Gaudens and possibly Roosevelt would have handled.”

The High Relief coins struck in November and December of 1907 were modified and about 12,000 were minted. The number was reduced in mid-December of that year, with the coin continuing in circulation through 1933.

A 1933 example on display at the New-York Historical Society is described as “one of the most famous and storied coins in the world.” The auctioneer says the 1907 coin’s unusual sans serif-edge font distinguishes it as one of the first struck that year at the Mint in Philadelphia.