This is an antique 19th century canvas mounted to wood painting of a depiction of Anne Boleyn, one of the most famous wives of 16th century British King, Henry VIII. The painting is based on the engraved print reproduction image from the 18th century of a portrait painting of Boleyn by Hans Holbein the Younger. Here is a link for you to a visual example of said print: https://i.ebayimg.com/thumbs/images/g/Eq4AAOSwvflZWlVp/s-l225.jpg
There is an underpainting image, that is more stylistically close to the print image. It was common in the later 19th century for paintings to be 'improved' or enhanced with a more ideal Victorian style face to modernize and update the art to the times. The 'new' painting appears to have been surface covered with a mastic varnish in the 19th century, which has proven that over time degrades and darkens the image. The estimate is based on the probable age, mastery and condition and does not factor in the underpainting.