This miniature portrait is signed "Gobert 1817". This is for Martial Gobert. His birth date was not known, although Schidlof suggested around 1800. However, as this miniature is dated 1817 and is believed to be the earliest signed and dated miniature by him, his date of birth seems likely to be pre 1800.
In fact from some research, he appears to be the Antoine Nicolas Martial Gobert, born around 1793, who married Mary Greenwood in Paris on 9 Dec 1818.
Their son, Alfred Thompson Gobert who was also a miniature painter was born 22 Sep 1822 and was christened on 14 Feb 1823 at the British Embassy chapel in Paris according to one record, and then on 20 Mar 1825 according to another. The second may have been a church christening, as required by the church.
Schidlof comments " Gobert was an artist of quality. His portraits are expressive, but sometimes lack relief, I (i.e. Schidlof) have seen at some time a miniature by him in which the clothes were of an exceptional execution and force."
The unknown sitter is likely to be French.
Literature: Les Peintres en Miniature p261. 1127