Proofs are pre-preproduction prints used to verify the quality of the printing process.  They are used from the earliest stages to test the printing plates as well as the final stages to confirm coloring and details for final production approval. Proofs, Progressive or Final, do not have serial numbers. They are not considered Error Notes.

Proofs used in the earlier stages of the printing process are known as Progressive Proofs.  These are generally missing most features that are recognizable in the final product.  They can be printed in various colors, use different paper, and include imagery that does not appear on the production version. Die Proofs, a type of Progressive proof, have been pulled from the Master Die stage of the printing process. Progressive Proofs are not intended for distribution to the public, but the ones that have made it to the public command significant value due to their rarity.

A Specimen Dollar is similar to a Proof and more commonly, a Final Proof. The only difference is that the Specimen is 'canceled,' meaning the Face Value is worthless. The Market Value, on the other hand, is of a greater value than the equivalent Proof and substantially greater than that of the equivalent Note produced for circulation.