Mark Hambleton, who went back to metal detecting after advice from his late father, made the find with Joe Kania on Staffordshire Moorlands farmland.
The three necklaces and bracelet, named the Leekfrith Iron Age Torcs, are believed to be about 2,500 years old.
Experts believe they were probably made in Europe, possibly Germany or France.
Julia Farley of the British Museum said: "This unique find is of international importance."
Dr Farley, the museum's curator of British and European Iron Age collections, said: "It dates to around 400-250 BC and is probably the earliest Iron Age gold work ever discovered in Britain.
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"Piecing together how these objects came to be carefully buried in a Staffordshire field will give us an invaluable insight into life in Iron Age Britain," Farley was quoted as saying by the BBC.
The four torcs were found separately, about 1m apart, buried near the surface in Leekfrith last December.
Hambleton said: "I was just about to give up for the day when Joe said he thought he had found something.
"We both looked at it and were speechless."
The jewellery has been handed to the Portable Antiquities Scheme, which is part of Birmingham Museums.
An inquest will decide whether the pieces are treasure and they will then be provisionally valued.
The friends said they would share any proceeds with the family living where the finds were made.