The use of surface relief holograms to create striking visual effects on coins is not necessarily a new technology, but one that is a challenge for circulating coins because of durability.
Holograms are effectively a structure of micro-gratings created through laser interferometry that display depth, colour and movement through the phenomenon of diffraction. They are applied to coins in one of two ways. First, and more traditionally, is the application of a resin or polymer on the surface of the coin to which the holographic microstructure is applied with a high elastomer stamp. The second is the engraving of the micro-gratings into certain parts of the stamping die to create a holographic element within a larger design.
In a sense, holograms on coins are not dissimilar to latent images, which are also a composition of fine lines that are engraved into the coin die, in that both show different effects according to the viewing angle.
In the case of holograms, however, the effects are dependent on exceptionally small and precise microgrooves. When these microgrooves start degrading – as they are wont to do both in the minting process and when handled – so does the image. Hence holograms are not suitable for large volume production, nor high circulation use, even though they do offer an added level of security (they are widely used to protect banknotes and other high value documents). But they do have benefits for collectors coins and bullion products, in the latter offering a mark of authenticity along with visual appeal.
At the Holography Conference Online held last November, holographic and numismatic Prof Hans Bjelkhagen described some of those coins, summarised below.
The world’s first holographic coin was produced for the Isle of Man in 1996 by Pobjoy Mint, a platinum ‘noble’ featuring a Viking ship in which the sail is picked out in a patterned hologram. Since then, a large number of holographic coins, medals and bullion products have been issued around the world.
They include the 2006 10,000 riel Taj Mahal coin as part of Cambodia’s ‘The Wonders of the World’ and produced by Singapore Mint, the 2012 one-dollar Space Station MIR coin produced by JSC Holography Industry and engraved at the Lithuanian Mint for Niue, and the 2000 3,000 forint silver coin commemorating the 100th anniversary of the birth of Dennis Gabor (the Hungarian inventor of holography) issued by the National Bank of Hungary.
One of the latest commemorative holographic coins to be released is the CZK 500 featuring an embossed hologram which depicts the Škoda 498 Albatros steam locomotive. Issued by the Czech National Bank in June last year, the hologram was created by Czech company IQ Structures.
The country that has led the way with holographic coins is Canada. The Canadian Gold Maple Leafs coin is one of the most popular gold bullion coins, with a holographic version first released in 1999 to commemorate the 20th anniversary of its gold maple leaf programme. The coin received the ‘Excellence in Holographic Product’ award from the International Hologram Manufacturers Association (IHMA) in the same year.
Further RCM coins commended with an IHMA award – for ‘Best Applied Decorative or Packaging Product’ – were the silver Canada Space Coin and five-ounce silver Lustrous Maple Leaves Coin. The Canada Space Coin was released to commemorate the 25th anniversary of the Canadian Space Agency in 2014 and featured an achromatic hologram of the International Space Station’s robotic arm and an astronaut. The coin was the second achromatic hologram coin produced by the RCM – created with nanotechnology-based imaging – with the world’s first introduced by the RCM in 2013 as a tribute to the 75th anniversary of Superman.
Likewise, the five-ounce silver maple leaves coin was the first of its type to feature a hologram in 2015, with the Canadian national symbol of the maple leaf incorporated as the hologram and struck directly on the coin.
Other Canadian coins featuring maple leaves include the 2001 $5 silver coin and $10 gold coin which both feature maple leaf holograms created with a high resolution dot-matrix design struck directly on the coin. The RCM also issued a 15-coin series in 2010 to commemorate the Vancouver Winter Olympic and Paralympic Games, with the holographic element highlighting the side of the coin depicting various winter sports.
Another notable issuer of holographic coins is the Royal Australian Mint (RAM). The A$5 coin released in 2001 is believed to be the first two-channel hologram coin, featuring the Federation Rotunda or a map of Australia depending upon the angle of view. The hologram utilised a method pioneered and patented by the country’s Commonwealth Scientific & Industrial Research Organisation (CSIRO), namely Replica Micro Molding, whereby the hologram side of the coin is coated with a resin and then the hologram embossed. This method was utilised in the creation of a proof only set in 2004, featuring holographic kangaroos.
In 2002, RAM produced the first three-channel silver A$5 holographic coin, featuring Kata Tjuta rock formations, for the ‘Year of the Outback Finale’. With improved technology, the hologram occupied almost half of one side of the coin.
In his presentation, Prof Bjelkhagen also talked about a new generation of holographic coins – namely, bitcoins. Even if cryptocurrency is digital, physical bitcoins still exist. As do holographic versions, albeit that the holographic element is not struck or etched into the coin. Instead, each coin has its own bitcoin address and a redeemable ‘private key’ printed on a card that is embedded inside the coin and covered up or protected by a tamper-proof hologram applied to the surface.
Given the need for mints to innovate (particularly those that rely on commemorative coins for a large part of their output), together with the reduced number of available technologies for making coins resistant to counterfeiting compared to banknotes, holograms could provide a solution – if and when the technical issues relating to durability are overcome.