The x-ray in the centre and the infrared reflectogram on the right show a change to the arm on the left's outline. In x-ray, the pale dense area in the hand on the left may be a book ribbon that was painted over, whilst the infrared image shows a ring or clasp on the end of a ribbon over the hand on the right. Freehand drawing is evident in the fur and the sleeves. The word 'rot' (red), in the cushion appears to be written in a wet medium, probably as a reminder to the painter or assistants.
© National Portrait Gallery, London