A couple who have made high-quality facsimiles of illustrated medieval manuscipts and even of the Dead Sea Scrolls have embarked on their most difficult challenge yet - to make a replica of the mysterious Copper Scroll.

The 2,000-year-old metal object, discovered in one of the Dead Sea Scroll caves in Qumran in 1952, appears to be a treasure map giving clues to the location of precious artefacts from the Temple in Jerusalem.

After two years of trial and error since beginning their attempt, Michael and Linda Falter of Facsimile Editions, London believe they have at last cracked it.

"Every single project we do ends up being more difficult than the last," said Mr Falter. "And it is certainly the case with this."

The original, now in a museum in Amman, Jordan, was so corroded that it was impossible to unroll at first.

The Falters used high-grade 3D scanners to produce moulds from three plates produced from the original by the French company, Electricité de France.

The plates were "a very accurate reproduction," Mr Falter said. "But they didn't look like an old artefact. So we were asked by the Dead Sea Scrolls Foundation if we could make something like the original."

But the couple's first attempts proved frustrating. "The metal was so thin that, as soon as you started using the chemicals you need to get the patina, they destroyed it," Mr Falter said.

Finally, they hit on a process which produced sheets which matched the French plates but with the more authentic green colour of oxidised copper.

The task will take around four months to complete. The plan is to display the finished article in a museum in the United States.

"When someone comes across it in the museum, they will be transported back 2,000 years and feel as close to it as the original scribes and artists had been," Mr Falter said.