The halfcrown (or half crown) was a denomination of the pre-decimal Pound Sterling coinage worth one-eighth of a pound, or two and a half shillings (a full crown being defined as five shillings), or 30 pence. In sums, it was abbreviated "2/6" (pronounced "two and six" - two shillings and six pence, a full shilling being twelve pence). The half crown was first issued in 1549 in the reign of King Edward VI.
This third type of halfcrown coins struck during the reign of King George IV was issued between 1824 and 1829. Its reverse design by Jean Baptiste Merlen is more ornate than that of the earlier types; the obverse has a new portrait of the king, also by Merlen.
After the king's death in 1830, the design was replaced by King William IV's halfcrown ; the practice of the time was to re-design the coinage for a new monarch's reign. At this time, the designs of the halfcrown and the smaller denominations started to diverge - earlier, the halfcrown, shilling and sixpence looked identical but with this issue they became different.
The composition is Sterling Silver (0.925 silver) and the coins have 0.4205 oz ASW (ounces of Absolute Silver Weight). The half crown was demonetised (ahead of other pre-decimal coins) on 1 January 1970, the year before the United Kingdom adopted decimal currency.