The lid of a large limestone coffin was lifted by eight people to reveal a smaller lead coffin inside. The lead coffin has gone to the University of Leicester's School of Archaeology and Ancient History for opening and laboratory testing.
King Richard, who died in the Battle of Bosworth Field in 1485, was hastily buried by Grey Friars. Although many people may be buried at the site of the former Grey Friars Church, archaeologists say this is the first time they have seen a lead coffin within a stone coffin.
"None of us in the team have ever seen a lead coffin within a stone coffin before," said Grey Friars site director Mathew Morris. "We will now need to work out how to open it safely, as we don't want to damage the contents when we are opening the lid."
Researchers suspect the remains could belong to one of three prominent people known to be buried at the friary. Two are leaders of the English Grey Friars Order; Peter Swynsfeld and William of Nottingham, who died in 1272 and 1330 respectively.
The other possibility is "a knight called Mutton, sometime mayor of Leicester," according to church records. Researchers believe the mayor referenced was the knight Sir William de Moton of Peckleton, who died between 1356 and 1362.
Researchers also hope to find the headless remains of three Franciscan friars hanged and then beheaded for treason on the orders of Henry IV, in 1402. Roger Frisby, Walter Walton and John Moody were accused of spreading rumors that King Richard II was still alive, and planning to retake the throne.
The friars' decapitated bodies were put on display in Oxford and London Bridge before being lost. Some historians believe the remains were claimed and buried by sympathizers at the Grey Friars dig site.