An early 19th century Russian Royal presentation brooch pendant

An early 19th century Russian Royal presentation brooch pendant, the circular brooch pendant with diamond-set 'A' beneath a coronet on blue enamel ground, with gold foliate border and set within a surround of old cushion-shaped diamonds in silver on gold, with a hinged enamelled gold pendant bail, inscription to reverse 'This Locket and a pair of Earrings were made from a box presented by The Emperor Alexander of Russia in 1812 to R. Adm'l Thomas Byam Martin for the defence of Riga, and other services in the Baltic', 6.5cm high (including bail), fitted case by Sheppard, Goldsmith & Jeweller to the Queen, 63 Brook Street, Hanover Square, London

The 'A' monogram refers to Alexander I, Tsar of Russia (1801 - 1825)

Literature: illustrated Scarisbrick, D., Jewellery in Britain 1066 - 1837: A documentary, social, literary and artistic survey, pl. XLIX