A coin collection that spent 50 years buried underground is set to become the most expensive numismatic coin collection ever brought to auction

The so-called 'Traveller' collection has an insurance value in excess of $100million, with the coins set to go to auction over the next three years.

A coin collection that spent 50 years buried underground is set to become the most expensive numismatic coin collection ever brought to the entirety.

The so-called 'Traveller' collection has an insurance value in excess of $100million, with the coins set to go to auction over the next three years.

The first of the auctions by Zurich-based Numismatica Ars Classica is set to take place on 20 May. The auction will be held at the Hotel Baur au Lac in Zurich.

The coins, of which there are around 15,000, come from as many as 100 countries across the world and range from modern coins to those from ancient times.

Arturo Russo, director of Numismatica Ars Classica, said: 'The vast range and superb quality of the coins offered, the sheer number of great rarities and the fascinating story of the collection's formation will make these sales a landmark in the history of numismatics.'

The prize piece of the collection is a 100 ducats coin minted in 1629, during the reign of Ferdinand III, archduke of Austria, king of Hungary, Croatia and Bohemia

The collector began to assemble the collection after the Wall Street crash in 1929, spending the 1930s travelling across Europe, and North and South America, building a detailed archive of each coin purchase.

In the late 1930s, the European collector buried the collection in aluminium boxes in order to hide them from the imminent Nazi invasion.

After the collector died during Nazi occupation, the coins remained buried for more than 50 years before they were eventually retrieved by the collector's descendants.

With the location of the coins known only to the collector's wife, they were left undisturbed until the 1990s, when she revealed to her family where the stash was buried and the coins were finally unearthed and stored in a bank vault.

The extensive cataloguing by the collector, and the coins' meticulous storage, means that the coins are 'in a state of preservation never seen in modern times,' according to Numismatica Ars Classica.

In fact, many of the coin types heading to auction have never before been offered at a public auction.

The prize piece of the collection is a 100 ducats coin minted in 1629, during the reign of Ferdinand III, archduke of Austria, king of Hungary, Croatia and Bohemia.

The fine gold coin, weighing 348.5g is one of the largest denominations of European gold coins ever minted and has not been seen at auction after the second world war.

Numismatica Ars Classيقة expects the coin could sell for an eye-watering £1.05million at auction.

The first coins set to head to auction are British machine-struck pieces from Charles II's reign up to a specimen set minted for George VI in 1937

Ancient: The oldest coin, an Athens gold stater from 296BC has an estimated value of £109,515.

The series consists of a 50 Toman coins minted in Persia, weighing just over 400g of gold

This Australian Port Phillip coin, minted by the ‘Kangaroo Office’, one of the earliest mints created to establish an Australian currency, could be worth over £200,000

A 1621 70 ducats coin of Sigismund III of Poland is estimated to fetch £394,260, while a five guinea of George III from 1777 is estimated to sell for £262,900.

Meanwhile, the oldest coin, an Athens gold stater from 296BC has an estimated value of £109,515.

The first coins set to head to auction are British machine-struck pieces from Charles II's reign up to a specimen set minted for George VI in 1937.

The auction will also see a £5 Una and the Lion coin by William Wyon, set to fetch an estimated £218,921.

David Guest, director of David Guest Numismatics, and consultant to the collection, said: 'When it came to cataloguing the British coins from the Traveller Collection I had to keep pinching myself to make sure I wasn't dreaming.

'Not only was the quality exceptional but many of the coins before me were of types not known to have been offered for sale in over 80 years and, in some cases, completely unrecorded.'