$20 NCR appears as a paper bill similar to a US $20 bill. It features a picture of First Ranger Seth on the face and the emblems of the NCR Rangers on the back.
As with any form of currency in Fallout: New Vegas, $20 NCR is not affected by the Courier's Barter skill. The currency will always be valued at 8 caps, regardless of whether the Courier is buying or selling.
A cut version of $20 NCR exists in Fallout: New Vegas' resources. It is a non-currency item, meaning its price is affected by the Courier's Barter skill. It is otherwise identical to the standard bill.