A SEEMINGLY ordinary married couple are believed to be the masterminds behind a daring £123million art heist.

Willem de Kooning's revered Woman-Ochre painting, which was stolen from the University Of Arizona Museum Of Art, was found “hidden” in the bedroom of Jerry and Rita Alter at their home in New Mexico.

The painting vanished on November 28, 1985, and while the suspects were described as a man and woman in their 50s, the case remained unsolved for 31 years.

Valued at an astonishing £123m ($160m), the famous art work was bought by the owner of an antiques shop in New Mexico in 2017 for £1,500 ($2,000).

David Van Auker, who co-owns Manzanita Ridge Furniture and Antiques, was completely unaware that he had an iconic piece of art history when he purchased the painting at an estate sale.

The Woman-Ochre was on offer along with other household possessions that belonged to Jerry and Rita – who died in 2012 and 2017 respectively, both aged 81.

After being tipped off by the knowledgeable customers at his store, that his new painting looked identical to the famous stolen art work, Van Auker contacted the FBI and the museum in Arizona.

Federal super cops are still investigating the case, but clues have started to emerge about the Alters’ alleged double life, reports local media.

The couple, described as “frugal” by their nephew, kept a day planner where they mapped out everything they did, from what they ate to the medication they took, reports KOB 4.

However, the entry for Thanksgiving 1985, the day of the robbery, was left mysteriously blank.

A family photo shows that Jerry and Rita were in Tuscon, Arizona, the day before the heist.

The couple, who have a son and a daughter, also fit the description of the two people who walked into the museum as its doors were unlocked the morning of the robbery.

Walking in behind an employee, the woman reportedly stood and spoke to the security guard while the man walked into the museum.

The building was officially open so the guard did not think to stop the middle-aged gent.

Around 15 minutes later the couple left in a hurry and sped away in a red sports car.

There were no security cameras in the museum at the time and no fingerprints were found.

Museum staff quickly realised that the Woman-Ochre had been cut from its frame.

Artist impressions of the suspect do bear a striking resemblance to the Alters.

The case remained cold until August 2017 when antiques dealer Van Auker found the painting “hidden” behind the master bedroom of Jerry and Rita.

He said he thought he had found a “great, cool mid-century painting” and paid the Alters’ nephew Ron Roseman £1,500 for it.

Roseman was unaware of the painting’s significance, according to reports.

The art work is back in the hands of the museum although it is still not on display.

Museum curator Olivia Miller told Silver City Daily Press: “I couldn’t believe I was looking at it in person. I’ve only known it through photos. I was trying to soak in every detail of the texture of it.”

More clues have now emerged connecting the couple to the robbery.

According to The New York Times, Jerry, who was a teacher and a musician, wrote a short story about a woman and her granddaughter stealing an expensive gem stone from a museum.

Written before he died, in what could have been a possible confession, the story also involves one of the characters distracting the security guard while the other snatches the gem.

The fictional duo in the story also speed away in a sports car.

Another potential clue, is that Jerry and Rita enjoyed travelling and visited an incredible 140 countries around the globe despite friends and family saying they did not have a lot of money.

But following their deaths, it was revealed that the Alters had more than a million dollars in their savings accounts.

Roseman, along with other relatives and neighbours, simply believed the couple lived “very frugal lives” which enabled them to indulge in travelling.

Another mysterious element to the story is the Alters’ children.

The couple had a son, named Joseph M Alter, and an unnamed daughter who police have been unable to track them down, according to reports.

Joseph, who was aged 23 in 1985, reportedly suffers from mental health problems and has spent much of his life in institutions

Several sources close to the family have claimed they owned a red sports car, reports The New York Times.

The FBI has refused to comment on the case while investigations are ongoing.