The coin is an 1804 Crown Five Shillings/ Dollar which was hung round the neck of a boy called John Johnson who joined the Northumberland Militia soon after we declared war with the French (1803) during the Napoleonic wars. In 1805 he volunteered to join the 7th Regiment - the Royal Fusiliers. He was sent to Dublin in 1806, then to Copenhagen and took part in the battle of 1807, by which time he was a Sergeant.
The Battalion then went out to the West Indies to blockade the French colonies. On the 25th Jan 1809, age 25, he was promoted to Sergeant Major for the Battalion, and this was inscribed on the coin. On the 28th, the fleet sailed from Barbados to invade Martinique. The island surrendered on Feb 24th.
Added to the coin in another style is D. 2nd March 1809. The records give his death as sickness - probably yellow fever. His effects were sent back home to his father, and have been passed on down to me.
The coin itself is interesting. Due to a shortage of silver,it was originally a captured Spanish coin, overstamped by the Royal Mint. Older readers will remember the pre-decimal half-crown coin, which we also called a half a dollar (2/6 - 12.5p)