Wonderful royal blue guilloche enamel  chunky little oval locket back pendant with inscription for a Captain of the Royal Navy and Naval Aide-de-Camp to Queen Victoria.
The front is decorated with a fouled anchor - applied gold set with small natural pearls - set at a jaunty angle. 
The back has a glass locket panel, now lined with a cream silk. Around the glass on the gold border there is the following inscription - 
‘ Captain J. Robb R. N. (Royal Navy) 
Ob 20th August 1859, Aet 55’ 
Captain Robb served extensively during the Napoleonic Wars. He was highly commended for his role in the boat action at the fortress of Bona (May 1824) and commanded a tender at the Battle of Navarino (1827).
In July 1857, he was appointed Naval Aide-de-Camp to Queen Victoria.
Captain Robb passed away at the age of 55 in Hampstead, London on August 20, 1859
He captained the HMS Gladiator (a steam-vessel) and took part in the Crimean War (1854). He also conducted experimental cruises with the Royal Yacht Victoria and Albert
weighs - 7.4g
measures - 22.7mm x 18mm (not including bail) 
English 1859
15 - 18 carat gold, enamel and natural pearls. 
condition - excellent. Small hairline in glass on back