Do you know how significantly an appraiser must dock a work of art lacking a signature?
Why do you want to find out?
If the artist is living, arrange to have them sign the artwork or generate an authorship letter with an image of the artwork shown on the same page as the artist’s affirmation that he/ she created that artwork.
If the artist is dead, find out who is the leading authority for the artist’s work. Contact that individual or that committee and meet their requirements to obtain an opinion letter.
One word of caution, more than one authority or committee for an artist’s work will have you sign an agreement stating they can destroy any work of art deemed a fake. Not everyone is comfortable with that requirement, to put it mildly.
Corinne Cain of www.SavvyCollector.com