Proof coins are struck by the Royal Mint especially for collectors, who appreciate them for their quality of craftsmanship. Though featuring the same designs as their circulating equivalents, the difference in appearance between proof and circulating coins could not be more apparent.
The making of the special dies begins when a rubber mould is taken from the artist's plaster model and a metal electrotype is formed by a process of electrolysis. The features of the electrotype are reduced on a reducing machine which, like a pantograph, traces the contours of the design and simultaneously cuts these same contours at a reduced scale into a piece of soft steel.
This steel punch, on which the design has been reproduced at coin size, is hardened by heat treatment and then used to sink a matrix. The matrix is the master die from which working punches are raised and from which, in turn, the working dies are made.
As well as the very latest modern technology, the hand skills of Royal Mint craftsmen still play a vital role, especially in the manufacture of the dies for collector coins. Experienced engravers, for instance, ensure that the artists design is portrayed to best effect and have the task of removing any imperfections from the master dies.
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The dies for Proof coins are specially treated to achieve a distinctive finish. Parts of the surface are highly polished with diamond paste, while relief areas of the design are frosted to provide a dramatic contrast to the remaining mirror-like background.
For Proof coins only virgin materials are used so that the cast metal is free from impurities. The blanks are thoroughly cleaned and polished by burnishing so that they are absolutely free from blemish before both dies and blank are brought together in the dust-free atmosphere of the Proof Coin Unit. To achieve perfect clarity of design, each blank is struck individually and receives at least two blows to ensure that all the details of the design are faithfully reproduced. The dies, too, are checked at regular intervals to eliminate flaws and blemishes.
Finally, highly trained inspectors examine each new coin and only the best are allowed to reach the packing section where they are placed by gloved hand into protective capsules, which are themselves placed in beautiful presentation cases. Highly-prized, these coins are much sought-after by collectors the world over, their promotion, sale and despatch being undertaken by the Royal Mint Coin Club.
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