This is the same as unknown artist.
It might happen that an artist or maker is unknown. As well you can find the following description:
•“Attributed to ….” In their opinion probably a work by the artist, at least in part
•“Studio of ….” or “Workshop of” In their opinion a work executed in the studio or workshop of the artist, possibly under his supervision
•“Circle of ….” In their opinion a work of the period of the artist showing his influence, closely associated with the artist but not necessarily his pupil
•“Style of ….” or “Follower of ….” In their opinion a work executed in the artist’s style but not necessarily by a pupil; may be contemporary or nearly contemporary
•“Manner of ….” In their opinion a work in the style of the artist but of a later date
•“After ….” In their opinion a copy (of any date) of a work of the artist
•“Signed…”, “Dated….” or “Inscribed” In their opinion the work has been signed/dated/inscribed by the artist. The addition of a question mark indicates an element of doubt
•"With signature ….”, “With date ….”, “With inscription….” or “Bears signature/date/inscription” in their opinion the signature/date/inscription has been added by someone other than the artist
Some works are not to be determined by whom it is made or it is made by (a group of) craftsmen. Examples are statues from the Ancient Time, furniture, mirroirs, or signatures that are not clear or readible but as well some works are not signed at all.
