This unsigned miniature portrait is very large for a miniature on ivory, being 170 mm x 130 mm. It has been attributed to Thomas Story Officer (1810-1859) who worked in New York, Philadelphia and a number of other cities before moving to Australia around 1850. He then returned to San Francisco where he worked until his death.
The portrait may be signed on the rear, but has not been removed from the frame.
Although not shown here, the heavy metal frame and matt are identical in size and style to that used for the portrait by Officer in the collection of Linda and Raymond White, now located at the Cheekwood Musuem. That frame is illustrated on the rear cover of the 1996 exhibition catalogue of the White collection.
Another miniature in the collection that has also been attributed to Officer can be seen at Officer, Thomas Story - portrait of two children
The sitter is Dr Amos Gerald Hull (1810-1859), who was a well known practioner in homeopathy and he also wrote on the subject. For more about him see Amos Gerald Hull and Amos Gerald Hull (1810-1859) - Pioneers of homeopathy by TL Bradford 903