The world’s most valuable type of coin has been accumulated by a real estate developer in Texas during the early years of the United States and is currently being auctioned with an estimated value surpassing $220 million.

The world’s greatest private collection of coins is expected to sell for $220million (£150million) in a record-breaking series of seven auctions at Sotherby’s and Stack’s Bowers Galleries.

Gathered over more than 30 years by Texas property developer A. Mack Pogue and his son, D. Brent Pogue, the collection contains coins from the early years of the American republic, from 1792 to the 1830s.

These are the most sought-after U.S. coins in existence, as the crude production techniques of the period meant that the coins were fragile, making surviving high-quality examples are extremely rare.

A treasure trove: An extraordinary 1822 five dollar gold coin, worth $8million, is up for auction. Pictured heads (left) and tails (right)

Intricate: An 1804 silver dollar piece, pictured heads (left) and tails (right), the most famous American coin in the world, is worth $8 to $10million

The Pogue collection includes two examples of the coveted 1804 silver dollar, considered to be the most famous coin in America, which is known as ‘the pinnacle of coin collecting’.

One of these is valued at $9.8million (£6.7million). Notably, it was presented to the Sultan of Muscat in 1835.

D. Brent Pogue, from Dallas, Texas, has now decided to ‘cash in his cash’ by auctioning off more than 650 individual coins at a number of Sotheby’s and Stack’s Bowers Galleries sales over the next two years.

Experts expect the collection to sell for almost $220million (£150million), more than any other series of rare coins.

On Friday, Sotheby’s showed off the jaw-dropping collection at its saleroom in New Bond Street, London.

David Redden, Sotheby’s vice chairman, said: ‘To have the world’s most valuable private coin collection available for viewing and sale in our galleries is a huge privilege and a great responsibility.

‘Sotheby’s and Stacks Bowers have worked fruitfully together in the past, notably on the sales of the 1933 Gold Double Eagle for $7.6 million and the Dallas Bank Collection.

‘The D. Brent Pogue Collection will be a thrilling addition to that auction history.’

A highlight of the collection is a $5 gold piece, known as the 1822 Gold Eagle, which is thought to be one of three in existence, and the only one in private hands.

Considered the most desirable US gold coin outside of public collections, it is expected to sell for around $8.8million (£6 million).

The 1797 Half Dollar, considered the most beautiful and best-preserved example of a design used for only two years, is the most valuable half dollar in existence. It is anticipated to sell for $1.5million (£1million).

And the 1808 Quarter Eagle, which is a $2.50 coin, is also expected to sell for around $1.5million (£1million), which is 500,000 times its face value.The coin was previously owned by the Maryland banker Louis E. Eliasberg, Sr, and the early 20th Century beer magnate Virgil M. Brand, according to Catholic Online.

Half Eagle coins have been widely collected over the years by notable figures including the banker J.P. Morgan.

Most of the coins were made during a time when small mintages and crude production facilities at the Philadelphia Mint made the survival of any high-quality coins unlikely.

Each steel die used to strike coins in the early 1800s was painstakingly produced by hand, creating variations that are prized by collectors.

The first sale, by Sotheby’s and Stack’s Bowers Galleries, will be on 19 May and there will be six further auctions with the final sale in May 2017.

D. Brent Pogue, who assembled the collection with the help of his property developer father, described the sale as ‘bittersweet’.

He said: ‘I feel now is the time to pass the torch to a new generation of custodians, who can appreciate the legacy of these great American coins.

‘These coins conjure up many fond memories, and I hope the new owners will enjoy them as much as I have.’

Coin sales are driven by the economy, but Brian Kendrella, the president of Stack’s Bowers Galleries, said investors and collectors are also lured by the rarity, uniqueness, condition and historical significance of coins.

‘They are artefacts that speak to what was going on in the United States at the time these coins were made,’ he said. ‘That’s one of the main draws.’

With a dozen coins selling for $1 million or more in 2014, and the first gold coin struck for the United States fetching $4.5 million, the nonprofit Professional Numismatists Guild estimates the overall U.S. rare coin market to be worth about $5 billion.

Walter Husak, a retired aerospace entrepreneur based in California, knows just how lucrative it can be. A collection of 301 rare penny coins dating from 1793 to 1814, which he gathered over more than 13 years, sold in 2008 for $10.7 million – about double what he invested in it.

‘I never thought it would go up that much,’ he said. ‘There are a lot of people getting involved in coins.’

Barry Stuppler, secretary of the Professional Numismatists Guild, has seen plenty of changes in his 52 years in the coin business. He says that the market has been booming in recent years.

‘It is a combination of the economy coming back,’ he said, ‘and the fact that interest rates are very low.’

The internet, he said, also has been ‘a tremendous, tremendous source of new buyers and sellers of coins that we didn’t have 20 years ago.’

Demand for rare, investment-quality coins, graded and certified by the guild and the Florida-based Numismatic Guaranty Corporation, is high and supply is low.

‘The rarities do the best, particularly gold and silver coins,’ said Stuppler.

‘The Pogue Collection is extraordinary.’