When an Auction House does not have reasonable evidence to prove a piece's authenticity, it will be cataloged with the appropriate Attribution Qualifiers.
Below is a list of the terms that you will see that have these qualifiers and what they mean:
| Term | Definition |
| After | A copy or reproduction of an original work. Includes a poster or other print reproduction of a known work by an artist. |
| Attributed To | Strongly believed to be an artist's original work but unable to be proven. |
| By | An original work by an artist. Authenticity, via a signature, stamp, or certificate, should be made available upon request. |
| In the manner of | An original work in the style of a known artist, made at a later date. |
| In the style of | An original work in the style of a known artist, made during the same timeframe as the stylized artist. |
| Studio/Workshop of | An original work by an unknown artist working in the studio of the named artist. |
| Circle of | An original work by another artist created in the manner of, and a lifetime of, the named artist |
| Follower of | An original work by another artist created in the manner of the named artist either during or after their lifetime |
| Replica of | A work by the artist him/herself made as a replica of their own, previous original |
| Signed | A work bearing the original signature, mark, or initials of the artist as a hand signed by the original artist. If not hand signed by the original artist, differentiation must be made. Hand-signed prints are usually numbered |
| Stamped | A work bearing the original stamp or mark of the artist. If not stamped by the original artist, differentiation must be made. |
| Plate signed | A work where the signature, mark, or initials of the original artist are printed as part of the original art image. Typically the artist has placed their signature on an etching or lithograph plate. Reproductions/photocopies should not be marked as plate signed |