When looking at Disney Dollars you may run into versions called proofs. 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. These don't have serial numbers because they are from pre-production test printings. They are printed in sheets of 18 notes.  Many of these prints were a limited run of 25 of these sheets or less. Because of the rarity you may find some individual notes or sheets but typically there costly.

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.