Almost exactly 200 years after it was made, to commemorate the death of someone with the initials ‘I.W.’, a mysterious mourning ring has been discovered by a metal detectorist in a west Dorset field.

The man who found it Colin Spiller, a 44 year-old building maintenance worker from Chard, Somerset, said it was a "fantastic find”.

Mr Spiller was taking part in a metal detecting day with about 50 other enthusiasts in a farmer’s field in Burstock, near Beaminster.

The ring is expected to fetch up to £1,200 at Mayfair auctioneers Dix Noonan Webb, the international coins, medals and jewellery specialists, when offered for sale at auction on September 5 in London.

Mr Spiller, who has been a metal detectorist for 12 years, said: “I thought about keeping it but it would only have stayed in the back of a drawer.”

He will split the proceeds 50-50 with the farmer who owns the field where it was found.

Laura Smith, a jewellery specialist at Dix Noonan Webb auctioneers, who regularly sell discoveries by metal detectorists, said: “This ring is such a poignant find. Mourning rings were worn to commemorate loved ones who had passed away and one cannot help but

wonder who ‘I.W.’ was and what sort of life he or she lived.”

The ring is a gold band decorated on the exterior with stylized foliage and a ‘momento mori’ (reflection on mortality) skull relief decorated in black enamel.

Inside is a Latin inscription which translates as ‘I.W. died 9 April 1717 aged 71.’ Although the black enamel is chipped and worn, the ring is in remarkably good condition given that it may have spent much of the past two centuries buried in a Dorset field.

It was on 26 February this year – almost exactly two centuries after the death of the person commemorated by the ring – that Colin Spiller went into the field accompanied by his 15 year-old stepson Ashley Miner.

After an hour they received a strong signal on their detector and found the ring about four or five inches below the surface.

Mr Spiller added: "To be honest, I thought it was a modern piece at first because it was black and I did not know that this was enamelling.

“Then Ashley put his finger through the middle of the ring to clear out the earth and we saw the date. We did a ‘high five’.”

“I didn’t know exactly what it was until Laura Smith at Dix Noonan Webb advised me. It’s historic and the most valuable thing I have ever found. We have registered it with Taunton Museum and the Portable Antiquities Scheme and I will be splitting the money with the farmer. It has been a great experience and I am now looking forward to more days out detecting.”