Antique 18th-19th Century Imperial Russian Miniature Portrait of a Russian Duke

Antique, 18th century, Imperial Russian, beautifully hand-painted miniature portrait of Prince Grigory Grigoryevich Orlov (1734–1783), one of the most prominent lovers of Catherine the Great in Russia.
The Prince is depicted in armor, with an ermine slung over his right shoulder, a white cravat, with a blue moiré sash of the Imperial Russian Order of St. Andrew the First-Called across his chest, and with a medal of the Imperial Russian Order of St. Anna suspended from his neck on a red ribbon with a narrow yellow border.
At the top of the white cravat, near his right shoulder, is a signature of the painter in very fine lettering. Since the signature is under glass and the letters are very small, we cannot read the artist's name.
The oval miniature is mounted in a brass inner frame within a rectangular frame which is veneered with reindeer bone straps in a manner characteristic of the 18th century Kholmogory, works of artisans from the Arkhangelsk region.
The back of the miniature is covered with a tortoiseshell imitation.
 
CONDITION: The edges of the painting panel were reshaped in the past, paint on the edges with brown stain and flaked, some discoloration in the paint near the gentlemen's head.
 
MEASUREMENTS: Diameter of the frame: 12.3 cm x 10.5 cm (4.84 inches x 4.13 inches).
 
For the Kholmogory craftsmen's artworks, please see the links below:
http://viola.bz/kholmogory-bone-carving/
http://www.burghley.co.uk/collections/collection/a...
http://bag-auction.eu/product/lot-0344-russian-18t...