The painting of Williamson reproduced here (in black and white, unfortunately) is from 1838. At the bottom left-hand corner of the original one can see the words "J.W. pinxt, 15 Decr. 1838". When comparing it with the 'half-seas over' portrait, one can clearly see the same facial features - the eyebrows and nose, for example, are exactly the same. This leaves little doubt that the painting is genuinely of Williamson, just two years before his death.