It is an “Aerodynamic Auto” built by the Marten Aircraft Co in 1928. It was a one off built for a pilot. The pilot was famous flyer Billy Mitchell.
That's awesome!
Colonel William "Billy" Mitchel commanded an Air Wing in WWI. That's the man the famous B-25 Mitchel - Medium Bomber was named after.
They made the first strike back at Japan after the attack on Pearl Harbor, "Doolittle's Raid on Tokyo".