File:Continental Currency $50 banknote obverse (September 26, 1778).jpg

As listed by the the U.S. Currency Education Program at money illustrations, the Counterfeit Detection Act of 1992, Public Law 102-550, in Section 411 of Title 31 of the Code of Federal Regulations (31 CFR 411), permits color illustrations of U.S. currency provided:
1. The illustration is of a size less than three-fourths or more than one and one-half, in linear dimension, of each part of the item illustrated;
2. The illustration is one-sided; and
3. All negatives, plates, positives, digitized storage medium, graphic files, magnetic medium, optical storage devices, and any other thing used in the making of the illustration that contain an image of the illustration or any part thereof are destroyed and/or deleted or erased after their final use.
Certain coins contain copyrights licensed to the U.S. Mint and owned by third parties or assigned to and owned by the U.S. Mint [1]. For the United States Mint circulating coin design use policy, see [2]; for the policy on the 50 State Quarters, see [3].

Also: COM:ART #Photograph of an old coin found on the Internet