Currency

Currency in the 31st century, at least originating from the USA, seems to still be dollars. Most notes look just like they are today, and each one of them has the face of an important individual on it. The $5 note has Abraham Lincoln (ITWGY), the $10 note has Benjamin Franklin (3ACV11), the $20 note has a Blob, probably H. G. Blob, saying it is "legal tender" (BBS), the $300 note has Richard Nixon (4ACV16), the $500 note has Al Gore (2ACV07), and the $1000 note has, once again, Richard Nixon (3ACV11). The coins also seem to be similar to what they look like today.

25¢

 * Coolio

$5

 * Abraham Lincoln's head.

$10

 * Benjamin Franklin.

$20

 * A Blob, possibly H. G. Blob.

$300

 * Richard Nixon's head.

$500

 * Al Gore.

$1000

 * Richard Nixon's head.

Production
During the writing for "A Fishful of Dollars", the writers considered other forms of currency than dollars, including "quadloos", "bux" and "jules". But they probably decided against it to simplify things.