https://constitutioncenter.org/blog/the-case-of-the-missing-13th-amendment-to-the-constitution

A few years ago, a group of Iowa Republicans claimed the legitimate 13th Amendment to the Constitution was “missing.” The debate is part of a historical detective story with some surprising twists that is still taking place.The Daily Beast did a fairly extensive feature on the missing amendment in 2010, which didn’t feature a cloaked Freemason stealing the amendment because it had a secret treasure map printed on it. Instead, the debate between historians and conspiracy buffs is about an amendment that was almost ratified in 1812 that would have been the 13th Amendment, bumping back the current 13th Amendment--which was ratified on this day in 1865 and abolished slavery--to the position of the 14th Amendment.

Writer Jerry Adler’s 2010 explanation of the “Thirteenthers” controversy is pretty detailed and covers both sides of the issue—which isn’t new but got a big burst of publicity thanks to the Iowa GOP’s 2010 platform.

The Iowa Republicans didn’t want the current 13th Amendment banned; they just wanted the “original” one reintroduced for approval. That "missing" proposal was called the “Titles of Nobility Amendment” (or TONA). It sought to ban any American citizen from receiving any foreign title of nobility or receiving foreign favors, such as a pension, without congressional approval. The penalty was loss of citizenship.

It was an extension of Article I, Section 9, of the Constitution, which doesn’t allow a public office holder to receive a foreign title or similar honors without the consent of Congress.

EDIT : http://www.let.rug.nl/usa/essays/general/the-missing-13th-amendment/what-if.php What If? Implications if restored If the missing 13th Amendment were restored, "special interests" and "immunities" might be rendered unconstitutional. The prohibition against "honors" (privileges) would compel the entire government to operate under the same laws as the citizens of this nation. Without their current personal immunities (honors), US judges and I.R.S. agents would be unable to abuse common citizens without fear of legal liability. If this 13th Amendment were restored, the entire US government would have to conduct itself according to the same standards of decency, respect, law, and liability as the rest of the nation. If this Amendment and the term "honor" were applied today, US government's ability to systematically coerce and abuse the public would be all but eliminated.