Description

A special anniversary edition of the 50p celebrates the science behind the shape and featuring a privy mark.

50 years ago a revolutionary new coin entered circulation ahead of the decimal switchover. Half a century later it’s still a testament to the science behind its radical design. A special anniversary coin pays tribute to Hugh Conway and his team. Tasked with creating a coin easily distinguishable by touch and sight that would still roll smoothly, their perfectly engineered solution gave the world’s first seven-sided coin.

In 1967 the Deputy Master of the Royal Mint approached the Decimal Currency Board to ask for their advice on the introduction of a new coin. The Technical Member (and the only engineer) on the Decimal Currency Board was Hugh Conway. He had found in a mathematical textbook formula for a non-circular shape of constant breadth and asked the design office at Patchway, near Bristol, which normally worked on the engines for aircraft such as Concorde, Vulcan and Harrier to draw out the shape. However, this turned out to be a wavy-edged form with re-entrant sides which would not roll and which could not be measured easily. A designer, Colin Lewis, suggested a much simpler shape which in its basic form is an equilateral triangle with a small circle centred on each apex and with a larger circular arc centred on each apex but tangential to each of the two opposite small circles. A drawing was made to illustrate the proposal which was accepted by Hugh Conway. He chose seven sides as a compromise between too radical a shape, which might not be acceptable to the public, and having too many sides, which would make a shape visually difficult to differentiate from a circle. The shape was drawn out by Dave Brown and samples made from stainless steel by the Model Shop, together with a section of perspex channel with a bend to demonstrate that the "coin" would roll around corners and drop through gauging slots. The legend "50" was photo-etched (from a master drawn by Ray Gooding) on the faces of the samples since it had already been decided that the new coin would be the first coin of the new Decimal series.

Obverse

The fifth crowned portrait of HM Queen Elizabeth II facing right, wearing the George IV State Diadem and drop earrings.

The George IV State Diadem, officially the Diamond Diadem, is a type of crown that was made in 1820 for King George IV. The diadem is worn by queens and queens consort in procession to coronations and State Openings of Parliament. The piece of jewellery has been featured in paintings and on stamps and currency. It can be seen in the Queen's Gallery at Buckingham Palace.

ELIZABETH II DEI GRATIA REGINA FIDEI DEFENSATRIX means Elizabeth II, by the grace of God, Queen and Defender of the Faith.

Engraver: Jody Clark

·ELIZABETH II·D·G·REG·F·D·50 PENCE·2019
J.C

Reverse

A seated Britannia alongside a lion, accompanied by the value above Britannia, with the numeral 50 underneath the seated figure. A special privy mark next to the numeral 50 referencing the science behind its shape.

A special privy mark next to the numeral 50 referencing the science behind its shape. A spirograph-type design drawn from an extension of lines forming the 50p shape creates this unique privy mark.

Innovative marks around the reverse rim of the coin. The letters A to G are inscribed on each point and are joined by arced crossing lines – this is a minting first on a 50p coin.

Although the archetypical image of Britannia seated with a shield first appeared on Roman bronze coins of the 1st century AD struck under Hadrian, Britannia's first appearance on British coinage was on the farthing in 1672, though earlier pattern versions had appeared in 1665, followed by the halfpenny later the same year.

Engraver: Christopher Ironside

A B C D E F G
NEW PENCE
50

Edge

50 Pence

5th portrait, Silver Proof Coin
KM#
Characteristics
Type Commemorative Issue (Non-circulating)
Material Silver
Fineness 0.925
Weight 8 g
Diameter 27.3 mm
Thickness -
Shape polygon
Sides 7
Alignment Medal
Mint
Royal Mint

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