When a mysterious item goes into an auction with a top estimate of £300 and makes a handsome £850, that's a Big Earner in anybody's book.

And that's what happened at Chorley's sale at Prinknash Park a few days ago, when this medallion with an intriguing background was in strong demand.

It was a Stonehenge medallion, a rare piece struck for the Ancient Druids Universal Brethren to raise funds to help Thomas Muir, one of the Edinburgh Martyrs.

The "Martyrs to Liberty" were five men who were imprisoned for campaigning for parliamentary reform in the late 18th and early 19th centuries. They were accused of sedition and transported to Australia in 1794, being allowed to return some 15 years later.

In a monument to their honour on Calton Hill in Edinburgh, Muir heads the list of them, so he was presumably the most prominent.

Its design has been attributed to William Blake, who had not in fact seen Stonehenge but apparently used drawings by William Stukeley as his model. The antiquarian Stukeley led excavations at the Wiltshire site in the 18th century.

Blake is thought to have visited the men aboard the hulks while they awaited transportation to Australia.

The sale of the silver medallion was a reminder once again of the way in which, in these changed ecomomic times, small items of intrinsic value seem to be realising higher prices than ever.

Prices for medals, coins, silver and jewellery are all buoyant, while fresh-to-the-market collectors' items are also in huge demand.

At the Chorley's sale, a "Newark shilling", produced by the Royalist forces under siege at Newark from 1644 to 1645 and used to pay the troops, fetched £700, while a small group of Scottish hammered coins – three groats and three pennies – also far exceeded face value at £1,000.

Traders' tokens from the 17th century onward, used as a substitute for currency at times when there was a shortage of coinage in circulation, were also avidly sought, with an album of them estimated at £200-£250 fetching £800 and another, with a £450 top estimate, racing to £1,500.

As for medals, the memorial plaque and World War I medals of Henry Watts Cash reached £750 – and here's a familiar story. What made all the difference was the presence in the lot of paperwork, including Cash's birth certificate and a photograph of him in uniform.