Unfortunately this miniature is unsigned, but it has been painted by a very talented artist. From the goatee beard and his costume, it would seem to date from around 1850/1860. Goatee beards were popular at different times, when there was also a moustache, it was usually referred to as the Imperial style, after the Emperor Napoleon III.
The detail of the sitter's head and clothing is painted with considerable skill. At first glance there appears to be some paint loss causing white splotches on his black neckchief.
However, as can be seen in the close up picture, the white marks are actually white stars that must be embroidered into the black material.
There are many miniatures in the collection from the mid 19C, where men are wearing black neckchiefs, but this is the only one where the neckchief is patterned.
From the close up image an interesting aspect of the artist's technique can be seen.
Instead of painting all of the collar white, the artist has left the collar area unpainted, so the natural ivory color shows through, and then he has used bright white for the highlights on the collar.
There were very few artists who could paint so skilfully that a painted miniature appeared to be a photograph.
John Henry Brown (1818-1891) of Philadelphia was the most famous of them and John Ramsier (1861-1936) of Kentucky was another. However, this portrait does not seem to be by John Henry Brown, as he usually signed his miniatures.
The date of this one does seem to be too early for John Ramsier, but John Ramsier did paint many copies of earlier daguerreotype and other images and when he did this, he seems not to have used a signature.
However, a more likely candidate is now thought to be John Alexander McDougall (1810-1894) who chiefly worked in Newark, NJ, but also worked in New Orleans, Charleston, SC and Saratoga Springs, NY. He also undertook portrait photography and was able to supply either painted or photographic miniatures.
Johnson comments; "McDougall remained active until about 1880, long after all the other well-known miniaturists except John Henry Brown had given up painting altogether in the face of competition from photography."
Johnson describes his work; "McDougall painted likenesses that were technically accurate, if somewhat dry and uninspired: they were typical of works of the mid-century in their deep, rich coloring, realism, and broad stippling. ...His works are rarely signed."
The sitter is unknown, but the miniature was acquired from Summerville, SC which is only 25 miles from Charleston, SC where McDougall had worked and so it is probable he received commissions from that area. 1275