The U.S. federal government stopped printing the $1000 denomination bills by 1946 and took them out of circulation in 1969. In 1960, it would have been appropriate for these bills to still be used for large transactions.
The images of the $1000 bills in the money clip look correct. A portrait of Grover Cleveland is on the front. Unlike most US currency there's no image on the back, but the words "United States of America" and "One Thousand Dollars" fill most of the space.
Singularly in this production, here the main star - Arthur Hill - is labeled "as" (The Man Who Found The Money) in the opening episode title "card" rather than (X person/persons appearing) "in" (X episode title).