A chance discovery during a sports event at the old Casemates prison has brought to light what could be an intriguing fragment of history.

“I thought it was a plastic toy at first,” said history buff Karl Outerbridge of a carved wooden lion that he said he spotted during a mountain bike race held on the historic site this month.

The carving is now in the hands of the National Museum of Bermuda, which cares for the historic building, originally a barracks for Royal Marines and built by convict labour in the 1830s.

Museum officials have no idea how the object came to be in the building.

Casemates became a prison in 1963 and then closed in 1995 when the nearby Westgate Correctional Facility opened.

Since then, Casemates has been meticulously checked over and photographed, making it highly unlikely for the eye-catching carving to have lain unnoticed for nearly 20 years. Mr Outerbridge said that he spotted it in a room inside Casemates as he looked for a spot to photograph the mountain biking event.

“The first thing I looked for was initials on it, but there aren’t any,” he said. “I grew up in Somerset and I knew a few people who ended up in Casemates for one reason or another. This could have been made by somebody I knew.”

Anyone who could help identify the carving or who can shed light on how it came to be in Casemates, can contact the National Museum of Bermuda at curator@nmb.bm.

Although the building has been thoroughly cleaned and surveyed, surprise finds have occurred before. In 2011, a team of volunteers helping to take apart the old prison bathrooms uncovered a wallet that had been stolen from a prison nurse 18 years earlier and hidden inside a wall.

Mr Outerbridge said he appeared to have a knack for finding unusual art.

“I have in my possession a painted sign that apparently came from the old Cock and Feather pub,” he said. “It was painted by the grandfather of Dominique Mayho, a top cyclist, around 40 years ago.”

Mr Outerbridge said he hoped the sign, which he bought at a sale of bric-a-brac, could be added to the collection at the Masterworks Museum of Bermuda Art.