Story highlights Archaeologists found a lead coffin within a stone coffin near Richard III's grave

The identity of its occupant is unknown, but there are three prestigious contenders

The confirmation this year of the discovery of Richard's remains drew global interest

The excavation site is at a parking lot in the central English city of Leicester

First came the dramatic discovery of the long-lost remains of King Richard III.

Now, there's the mystery of the coffin within the coffin.

Archaeologists working at the site in central England where Richard III's body was found underneath a parking lot are currently puzzling over a sealed lead coffin containing the remains of a yet-to-be-identified person.

The lead coffin was found encased in a larger stone coffin.

The smaller coffin is intact "except for a hole at one end of the casket through which we could tantalizingly see someone's feet," said Mathew Morris, the fieldwork director at the site.

New discovery just as exciting

Last year, archaeologists unearthed a body buried beneath a nondescript parking lot in the city of Leicester. In February, they confirmed the body was that of Richard III, the last king of England to die on the battlefield.

The news drew global attention and set off a debate over Richard's bloodthirsty reputation.

Photos: The remains of King Richard III Photos: The remains of King Richard III In 2012, experts began digging away at the area and established that it was part of the friary and that a skeleton, hastily buried in an uneven grave, was that of King Richard III, who was killed in 1485 during the Battle of Bosworth Field. Hide Caption 1 of 11 Photos: The remains of King Richard III Mitochondrial DNA extracted from the bones was matched to Michael Ibsen, a Canadian cabinetmaker and direct descendant of Richard III's sister, Anne of York. Hide Caption 2 of 11 Photos: The remains of King Richard III Scientists at the University of Leicester say their examination of the skeleton shows Richard met a violent death: They found evidence of 11 wounds -- nine to the head and two to the body -- that they believe were inflicted at or around the time of death. Here, the base of the skull shows one of the potentially fatal injuries. This shows clearly how a section of the skull had been sliced off. Hide Caption 3 of 11 Photos: The remains of King Richard III The lower jaw shows a cut mark caused by a knife or dagger. The archaeologists say the wounds to Richard's head could have been what killed him. Hide Caption 4 of 11 Photos: The remains of King Richard III A wound to the cheek, possibly caused by a square-bladed dagger, can be seen here. Hide Caption 5 of 11 Photos: The remains of King Richard III This hole in the top of the skull represents a penetrating injury to the top of the head. Hide Caption 6 of 11 Photos: The remains of King Richard III Two flaps of bone, related to the penetrating injury to the top of the head, can clearly be seen on the interior of the skull. Hide Caption 7 of 11 Photos: The remains of King Richard III The image shows a blade wound to the pelvis, which has penetrated all the way through the bone. Hide Caption 8 of 11 Photos: The remains of King Richard III Here, a cut mark on the right rib can be seen. Hide Caption 9 of 11 Photos: The remains of King Richard III As the skeleton was being excavated, a notable curve in the spine could be seen. (The width of the curve is correct, but the gaps between vertebrae have been increased to prevent damage from them touching one another.) Hide Caption 10 of 11 Photos: The remains of King Richard III The body was found in a roughly hewn grave that experts say was too small for the body, forcing it to be squeezed into an unusual position. The positioning also shows that his hands may have been tied. Hide Caption 11 of 11

JUST WATCHED The king in the parking lot Replay More Videos ... MUST WATCH The king in the parking lot 02:47

JUST WATCHED Tracking down Richard III's remains Replay More Videos ... MUST WATCH Tracking down Richard III's remains 02:30

JUST WATCHED The woman who found Richard III Replay More Videos ... MUST WATCH The woman who found Richard III 05:09

Archaeologists from the University of Leicester, who have been toiling away at the site this summer, say the discovery of the double coffin is just as exciting.

They only uncovered the lead coffin last week after eight people hauled the heavy lid off the stone coffin. But figuring out who's inside looks set to be a much tougher task.

"This inner coffin is likely to contain a high-status burial, although we still don't know who it contains," Morris wrote in a blog post . "No writing was visible on the coffin lid but it does bear a crude cross soldered into the metal."

There are three main contenders for the identity of the coffin's inhabitant: a medieval knight named Sir William de Moton of Peckleton, and two leaders of the English Grey Friars order, Peter Swynsfeld and William of Nottingham.

Beneath the parking lot

The Leicester site is where a church, known as Grey Friars Friary, once stood.

Over the centuries, the whereabouts of the friary's remnants were forgotten, but it remained in the records as the burial place of Richard III.

Last year, experts began digging away at the area, which had taken on the less illustrious role of a parking lot. They went on to establish that it was part of the friary and that a skeleton, hastily buried in an uneven grave , was that of Richard.

The archaeologists who undertook a new dig this summer think the double coffin, located near Richard's grave, was buried during the 14th century, more than 100 years before Richard was killed at the Battle of Bosworth Field in 1485.

Of the coffin's three likely occupants, Swynsfeld died in 1272, William of Nottingham died in 1330 and Sir William de Moton died between 1356 and 1362.

'A first for all of us'

Besides the puzzle of who lies within, the archaeologists were excited about the coffins themselves.

"This was a first for all of us on site," Morris said. "None of the team had ever excavated an intact stone coffin before, let alone a lead coffin as well."

They have now wrapped up their four weeks of digging at the site. The lead coffin has been taken away so that experts can carry out tests to figure out the best way of opening it without damaging its contents.

But, Morris said, other parts of the friary that the archaeologists tried to investigate this summer appear to have been completely destroyed -- meaning that some of the site's mysteries may never be solved.