A historic coin that dates back more than 700 years has been excavated at an archaeological dig.

Members of the Sussex Archaeological Society unearthed an Edward I silver farthing during the Battle of Lewes metal detecting survey on Sunday, May 19.

The oval-shaped silver farthing measures 12mm by 10mm and dates back to around 1300 to 1310.

Because the coin was issued during the transition between the last years of Edward I’s reign and the start of Edward II’s reign, researchers initially struggled to attribute it to the correct king.

But by using special identification techniques, like assessing what type of crown the king was wearing and the style of lettering on the coin’s inscriptions, experts believe the coin dates from the last seven years of Edward I’s reign, from 1300 to 1307.

Stephanie Smith, the society’s finds liaison officer, said the coin was probably dropped during everyday activity outside the town and not at the Battle of Lewes, which took place nearly 40 years earlier.

She said: “There are transitional issues between Edward I and the earliest coins issued by Edward II.

“The portraits on the coins are similar to each other so they can be difficult to identify.

“Some have inner circles, particular crowns, a particular way the hair is positioned and how they abbreviated their names and titles in the inscriptions.

“You can see why people lost farthings, as they’re so small and light. People used to wear open-pouch purses that hung from their belts, so if someone was hurrying to market and was in a rush, for example, it would have been quite easy to lose things like this.

“The person who lost it would have been annoyed, but not devastated.

“If they’d lost a groat, for example, they would be very cross, as it was worth a lot more.

“Farthings are regularly found throughout the UK but it’s the first we’ve found of its kind on the battlefield site.”

The society wouldn’t reveal how much the coin was worth, but a spokesman said its value was in its archaeological importance, not its market value.

Diggers also discovered a horse harness pendant mount and a strap-end used to decorate belts, both from the same period.

The Lewes Castle museum said it hopes to display some of the objects from the project in the near future.