The item in question is a specific type of United States currency. It is a one-dollar bill issued in 1957 that is redeemable for silver. These notes are identifiable by the blue seal and serial numbers printed on the face of the bill.
These notes hold interest for collectors due to their historical significance as representatives of a time when U.S. currency was directly tied to silver reserves. They also represent a shift away from this metallic standard, marking a transition in monetary policy. Depending on condition and serial number rarity, the value of these notes can exceed their face value.