A rare eightpenny coin from 1913 that never made it into circulation has come up for auction.

The coin, known as an Octorino, was one of only around 20 produced as a possible answer to a tricky National Insurance tax problem.

In May 1911, when the National Insurance Act was first implemented by the Liberal Government, employees had to pay fourpence of their weekly wage for future sickness protection.

Employers who had to deduct this awkward figure from their employees’ weekly salary were now faced with an issue –  that the coins they needed did not exist.

People were paid in shillings, worth twelve pennies, and in order to take four pence off this figure employers would need an eight pence coin.

With bosses bemoaning the additional time spent handling ‘thousands of odd coppers’, Captain Faber, a Unionist MP, asked in Parliament whether a new eightpenny coin, dubbed an ‘Octorino’, could be created to solve the issue.

However, plans never advanced beyond a trial stage.

Coin Specialist at Spink, Gregory Edmund said: "Basically the law came in, in May 1911, with the first contributions settled from July 1912.

"In Parliament in December 1912, the point was raised that an Eightpenny (Octorino) coin could be of practical use, but was quickly shot down by the Liberal Government of the day.

"Nevertheless a passionate coin collector named Reginald Huth took it upon himself to create trial coins, called “Patterns”, like this one, to sell to collectors in 1913.

"He made them in various metals from copper, to iron, weirdly made from recycled iron nails recovered from a Tudor Castle of all things.

"He also produced them in platinum and silver, like the one here, estimated at between 10 and 20 pieces before the dies were destroyed.

"Very few ever surface on the open market and this is the first we have handled since 2015.

"In short it was never an 'official' coin, but Huth was inspired by the public and economic discourse to experiment and produce his own, that sadly never entered circulation."

The collectable is expected to fetch at least £2,500 when it is sold.

Mr Edmund added: “Today, when physical money seems quite alien and the jangle of coins in our pocket is but a fond memory, collectable coins come to remind us just how connected to the past we really are.

“The Octorino is not a coin known to many, but its solution to the challenge of paying National Insurance is as familiar to us today as it was when experimented with over a century ago.”