A home-made metal detector, which works by remote control, has netted a father and daughter a haul of coins worth £2,000.
Demi Watkins says their invention saves time and effort
Decima Watkins' father David from Barry, Vale of Glamorgan, made it from scrap metal and recycled materials.
They say it can cover the ground automatically, and save on the more back-breaking work, combing for coins.
Art student Decima, 20, said after initial trial and error the detector, which cost £100 to make, has paid off.
They spent more than a year building the "Decima Detector" in Mr Watkins' garage and found a haul of old coins while trying out their machine.
They have collected more than £2,000 in cash on Porthkerry beach near their home, as well as finding 5,000 assorted silver and hammered coins, some they say date from the 14th Century.
Decima now hopes a company might be interested in developing the machine.
"It took around a year to make and it cost £100. We used recycled materials, visited scrap yards and went to tips to get hold of things," she said.
"It's even got rechargable batteries."
The remote detector also has lights on it and it can be taken out in the dark.
Decima, who has demonstrated the detector on YouTube, moves along the ground quite quickly and allows them to cover fields in hours rather than months.
It indicates when it picks up a signal suggesting there is metal beneath the ground.
They then have to dig a hole to retrieve the coins or bits of metal.
The Barry College student said she loved metal detecting and got the bug when she went out with her father searching for treasure.
"I can't believe we invented this and got it all running," she said.