The sketch---credited to me---is based on a painting in the Town Hall of Torun, Poland. Torun was Copernicus' home town. The painting is believed to have been done in the early or middle 16th century and may be the most authentic portrait. The artist is unknown. It's possible that the painting is a self-portrait or based on one since Copernicus is thought to have done a self-portrait. An image of the original and better description can be found at the Copernicus iconography site of Robert Derome, University de Quebec a Montreal.