You know how clothing stores prop up mannequins in windows, showing off the fashionable goods they have to offer? That might be the explanation behind a case of mistaken mummy identity.

During a trip to Egypt in the late 1850s, Sir Charles Nicholson — an English Australian antiquarian, university founder and philanthropist — bought a mummified body, coffin and mummy board, which he donated to the University of Sydney in 1860, according to a study published Wednesday in the journal PLOS ONE.

The mummy was a socially esteemed woman named Meruah, according to the coffin inscription that dates back to around 1000 BC. A separate group of researchers discovered the coffin's age in 1988.

The mummified body had been encased in a mud shell, or carapace, but that wasn't discovered until 1999 during a project led by Karin Sowada, the first author of the current study. That's because computed tomography scans had only recently become possible.

New technology allowed the researchers to perform virtual dissections and therefore better characterize the layers of the carapace around the body in 2017. That's when The University of Sydney was preparing to open its Chau Chak Wing Museum, "which has a dedicated space for the ancient Egyptian material of the Nicholson Collection," said Sowada, a research fellow in the department of history and archaeology at Macquarie University's main campus in Sydney, via email.

The shell's layers were made of minerals, which differed from the expensive resin used for mummified elite individuals. "This is the first time that a painted mud carapace treatment has been discovered," Sowada added.

Through analysis of samples from the mummy's linen wrappings, the researchers also found that the person lived in the late New Kingdom, in the Ramesside period from around 1200 BC to 1113 BC. That meant that the body was much older than the coffin.

"Many coffins were robbed of their original occupants in ancient times. It's likely that in the local antiquities trade of the 19th and early 20th centuries, many coffins for sale were empty," said Sowada via email. "Dealers obtained complete mummified bodies found in desert cemeteries and placed them in coffins to sell complete 'sets' to tourists, even though bodies and coffins may not have belonged together.

"It was fashionable for foreign tourists to return home with an Egyptian mummy."

Samples of DNA taken from the body about 15 years ago indicated that the person was a male, but the conclusion has shifted back to probably a female who had lived 26 to 35 years. The authors updated their conclusions by studying secondary sexual characteristics, which are features that appear when humans go through puberty, like when females might develop wider hips, or when males might grow more and thicker facial hair.

The body's internal reproductive organs had been removed during the mummification process, and genitalia weren't seen on the scans, so more detailed analyses of DNA samples are needed, Sowada said. "However, this would require further invasive engagement via destructive testing, and that needs to be carefully considered on a number of levels."

The shifting of determinations about a mummy's sex "happens all the time," said Peter Lacovara, the director of The Ancient Egyptian Archaeology and Heritage Fund and consulting curator for the Egyptian Collection at the Albany Institute of History and Art in New York state. "At the Albany Institute, we had a mummy that had been earlier identified as a female, and we took it to be tested and it turned out to be a male."

"It's sometimes harder to tell with ancient bodies; there seems to be less distinction, or we pick it up less clearly."

The DNA collected back then may have been contaminated, the authors said.

The body also experienced damage shortly after the initial mummification, including the separation and displacement of the cranium, the jawbone and parts of the spine. Some bones were far away from their rightful place — the left kneecap was at the level of the left ankle, and the right kneecap was below the top of the left thigh bone. Some bones were fractured.

"Mummification dessicates and stabilises the bodily tissues, so we would expect to see very little (if any!) post-depositional movement or disarticulation of any bones," Sowada said via email.

"The CT scans of this person's body shows us that they were subject to significant disruption — but also, importantly, that they were provided with a great deal of care to restore them after they had been disturbed."

The body was then subjected to rewrapping, packing and padding with fabrics, and the application of the mud shell. The mud carapace "likely fulfilled a threefold purpose," the study said. It was a form of conservation for a body that had gone through significant damage, for one, and may have served a symbolic purpose as well.

"The carapace aided the metaphysical transition of the deceased into the afterlife and the sphere of the god Osiris," the study said. "The mythological experiences of this underworld deity — his death, dismemberment, re-establishment and re-birth — had long been established to serve as a precedent for the mortuary experience of all Egyptians. ... Like the god, the deceased could also hope for continued existence in the afterlife, when properly prepared."

"Mud itself was associated with the idea of regeneration and growth," Sowada said, "so it would have been a symbolically significant material to use."

Lastly, because the minerals comprising the mud shell were options less expensive than the resin used for elite mummified individuals, they might have enabled the repairers to display status by emulating the mummification practices for elite people.

The red pigment used for the part of the shell covering the face was a bit uncommon for women mummified during that period.

"This practice relates to the belief that women took on a temporary, crucial, postmortem masculine aspect in death so that they could be reconceived and reborn into the afterlife via their own images (in the same way that male tomb owners were believed to undergo that process by means of representations of their female relatives or goddesses)," said Heather McCarthy, an Egyptologist and deputy director of the New York University Epigraphical Expedition to the Ramesses II Temple at Abydos, via email. "The use of masculine, red and red-brown skin tones is a pictorial signifier of that gender-fluid state."

The findings help to construct a bigger and more nuanced picture of how the ancient Egyptians treated and prepared their dead, Sowada said.

"It's likely that prior studies on mummified bodies in other collections, where a 'resin' carapace has been identified, will need to be re-examined for the possibility that the carapace is made of mud instead," she added. "The application of scientific techniques to museum collections reveals the wealth of new information sitting right under our noses."