Cooper's Handwritten Flight Certification

Along with the note, which I purchased at auction from the Cooper Estate, I also received the envelope in which the note was stored. On the envelope, Cooper had written: "This old 1917 issue $2 bill was flown by me in my flight suit pocket on MA9." It is wonderful to have hand-written flight certification on the bill itself, and on the envelope that held the bill...but to also know that the bill was not only on board the spacecraft, but was also on Cooper's person during the entire length of the flight is very unique and adds to the historic importance of this bill.