1. President Harry Truman is believed to be the first sitting president to use the modern autopen reguarly. eBay even had a Truman signed thank-you-note for sale, as Gawker noted. But Time Magazine said President Thomas Jefferson was a fan of the polygraph, a new invention at the time that recorded his signature.

2. Obama has used it before, including to sign an extension of the U.S.A. PATRIOT Act in May 2011 because he was in France at a G-8 Summit, CBS News reported at the time.

3. It’s legal. President George W. Bush commissioned  the U.S. Department of Justice to look into the auto pen’s constitutionality. The result: A 29-page opinion saying it’s legal. But Bush didn’t risk the controversy and never used it to sign legislation, according to ABC News.

4. While Bush avoided it, his Secretary of Defense Donald Rumsfeld didn’t. Rumsfeld was criticized in 2004 for autopenning condolence letters to families of soldiers killed in the Iraq war. One of the relatives told The Guardian at the time: “He had time for golf and the ranch but not enough to sign a decent signature with a pen for his beloved hero soldiers.”

5. There’s an entire book dedicated to the auto pen. In 1965, Charles Hamilton published “The Robot That Helped to Make a President,” about how President John F. Kennedy used the machine.

6. In 1992, Vice President Dan Quayle blamed a staffer for using the autopen to sign a letter asking for an imprisoned GOP donor be sent to a minimum security prison.

7. It’s more personal than a printer. That’s because presidents have different forms of signatures, including signatures that are digitally printed. White House officials told The Associated Press in 2011 that the autopen signature is generally used “for more personalized correspondence.”

8. Machines range from $2,000 to $10,000, according to The AP.

9. Former Enron chairman Ken Lay’s legal team argued in 2006 that Lay shouldn’t face banking charges because he didn’t sign some of the bank forms — an autopen did, Highbeam Business reported at the time. Lay was ultimately convicted.

10. Presidents Bill Clinton and Ronald Reagan had bills flown to Turkey and China, respectively, so they wouldn’t have to sign major pieces of legislation with the autopen, NPR reported in 2011.