Auction house Sotheby's is preparing for a major sale in mid-November in New York. An extremely rare official first-edition printed copy of the U.S. Constitution will go under the hammer on the 234th anniversary of its signing by delegates to the Constitutional Convention.

Sotheby's estimated its value at $15 million to $20 million.

"It's the official printing, the first printing of the final text of the United States Constitution done probably on the evening of the 16th of September, 1787, only for the use of the delegates to the Continental Convention and for the use of the Congress of the United States," said Sotheby's Senior Specialist for Books and Manuscripts, Selby Kiffer.

"This is the only one that is not in a permanent institutional collection."

It last sold for $165,000 in 1988, when it was acquired by the late S. Howard Goldman, a New York real estate developer and private collector of American autographs, historical documents and manuscripts.

His wife, Dorothy Tapper Goldman, is offering it for sale, with all proceeds going to the charitable foundation established in her name to further the public's understanding of democracy, the auction house said.

Copies from that first printing, bearing no signatures and believed to have originally numbered about 500, were furnished to delegates of the Constitutional Convention. Two surviving copies are housed at the Library of Congress.

The Constitution's first printing is considerably rarer than even the first edition of the 1776 Declaration of Independence, Sotheby's said.

It contains only the seven original articles laying out the framework for the U.S. national government and its powers, its relationship to the states, and procedures used to subsequently ratify and amend the Constitution itself.

The Bill of Rights, consisting of the first 10 amendments added to the Constitution, did not come until 1791.

Although not signed, the six-page document includes a list of the Constitutional Convention delegates attesting to its adoption in 1787 and a letter of submission from George Washington, who presided over the convention.

Regarded as the oldest, continuing codified government charter in the world, the U.S. Constitution was devised to replace the young nation's first, largely inefficient charter, the Articles of Confederation.

It was ratified by the states in 1788 and went into effect the following year. It has since been amended 27 times.

Sotheby's said the Goldman copy would be offered for bid at a New York event sometime in November.

"There were vivid debates about whether it should be ratified or not," Kiffer said. "And those debates continue today. It's the foundational document that's going to last, I think, long beyond the current political atmosphere."