The British pre-decimal penny coin, abbreviated as 1d (from "denarius" - the Roman coin from which the penny is directly descended), was a unit of currency that equalled one two-hundred-and-fortieth of a pound sterling (there were 20 shillings to a pound, and 12 pence to a shilling so one pound was equal to 240 pence).
The denomination continues the tradition of earlier penny coins of Great Britain, which also featured the figure of Britannia. The bronze coins of these specifications replaced the larger copper pennies which were issued until 1860. The new, more durable, alloy was composed of 95 parts of copper, four of tin and one of zinc. Between 1860 and 1895, the penny had the third Britannia design on the reverse, and Queen Victoria's "Bun Head" effigy. In 1895, the reverse was updated to this fourth Britannia design - which is a simplified version of the earlier design by Leonard Charles Wyon, and the obverse to the Queen's "Veiled Head" portrait. Unlike the smaller denominations, which were redesigned for the new coinage of King George VI in 1937 (see the Ship Halfpenny and the Wren Farthing), the penny did not get a new design and retained the classic Britannia reverse until the end.
During the reign of King George V, the mint had issues with the monarch's portrait by Sir Bertram Mackennal. Many of the bronze blanks used for the coins were produced by private firms in Birmingham. A great deal of difficulty was encountered in striking coins of this design. The high relief portrait caused a displacement of metal, called "ghosting", that showed through on the reverse side as an incuse outline of the head. A new bronze alloy was adopted in 1923 in an effort to remedy the situation. It consisted of 95.5 per cent copper, 3 per cent tin and 1.5 per cent zinc. This alloy has a more golden tint than the former one. It lessened the hardness, enabling the coins to be more easily struck and lengthened the life of the dies. During 1925 the features of the design were slightly modified to further help eliminate the "ghosting", but this fault was not fully corrected until 1928 when a new design, with a smaller head, was introduced. The coins with the modified effigy from late 1925 and thereafter all have the designer’s initials in small letters without periods.
One penny coins issued in 1951 remained in circulation for 20 years until "Decimal Day", 15 February 1971 when the old currency was demonetised and the decimal Pound Sterling was introduced, with a new decimal penny replacing these old coins.
The reverse of the coin shows, within a beaded border, the figure of Britannia - the female personification of Great Britain - seated facing right, wearing a crested Corinthian helmet pushed back to reveal her face and a flowing dress, resting her right hand on a shield bearing the combined crosses of the Union Flag, and holding a trident in her left hand.
In the background, sea waves and at left, a lighthouse.
Around left and right, the value and denomination ONE PENNY.
In exergue, the date 1951.
All one penny coins of 1951 have Obverse 3 and Reverse C (definitions by Freeman).
For information about Freeman obverse/reverse varieties, see descriptions on the one penny / fourth Britannia type page.
References to additional information:
[Book] Bressett, Kenneth E. 1962. A Guidebook of English Coins, Nineteenth and Twentieth Centuries. Wisconsin, USA. pp 31-40
[Book] Freeman, Michael J. 1970. The Bronze Coinage of Great Britain. Motherwell, Scotland. (2016 ed. pp48-73)
[Book] Remick, Jerome. 1971. The Guide Book and Catalogue to British Commonwealth Coins., pp 202-206