State Library of NSW
The portrait is very similar to a watercolour portrait of John Thomas Bigge by Thomas Uwins (P2/290) and an oil painting of Bigge by Uwins (ML 822).
All appear to be finished works. This ceramic and the oil painting more closely resemble each other. In the watercolour, the writing on the paper on the bureau, is denser; and the writing in Bigge's right hand is more detailed, than in either the ceramic or the oil painting.
It is not possible to say which work might have preceded the other but it seems possible the slightly more detailed watercolour might be the earliest work.
The ceramic is a highly finished work. It may have been painted by Uwins, known to have painted miniatures, or copied at a later date by another hand.
One edge seems to have been cut to size; paint can be seen on the edges, especially the cut edge. The ceramic panel is glazed front and back.
Unsigned and undated; dated from manuscript in painting.