The late 9th century silver brooch was discovered in a field in Great Dunham, Norfolk, which had recently been landscaped.
It is not known where the soil came from, but experts say the find is similar to the nearby Pentney Hoard, a find of six disc brooches in 1978 in West Norfolk.
The origins of a 1100-year-old brooch found in a lorry-load of soil is still shrouded in a mystery.
The brooch was found by an inexperienced detectorist on 9 May 2019. The silver disc, about three inches (7cm) in diameter, features a cross with concave arms, over a saltire, and is intricately decorated with animals in the Trewhiddle style, with a pin attached on the back.
An inquest, which should officially constitute the find treasure or not, will conclude on 9 June.
Prof Michael Lewis of the British Museum said it was “of national significance”.