The gold Janus cup suggested to be Archaemenid that sold at £50,000.

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They were offered for sale by John Webber, the grandson of Taunton scrap metal dealer William Sparks, who had acquired the items from different sources during the 1930s or early 1940s.

The three disparate pieces are seemingly without parallel in ancient metalwork, and laboratory tests undertaken by Oxford University failed to instill full confidence in either the dealing or the academic community. Mr Webber initially took the items to the British Museum who refused to pass judgment on them.

The principal item was a 5 1/2in (14 cm) high Janus cup suggested to be Archaemenid and dateable to the 3rd or 4th century BC. Metal analysis undertaken by Oxford Materials Characterisation Services of Oxford University concluded that the method of manufacture and the composition of the gold were consistent with Archaemenid goldsmithing, although it also found traces of cadmium, an element only identified in 1817.

While cadmium does exist naturally in minerals, it was not known to have been used in the solder on man-made metal objects until the 1820s.

Duke's, who estimated it might fetch £50,000-100,000, catalogued the cup without committing to an attribution. Partner Guy Schwinge pointed to this as he began the sale, saying: "Please note the description, and that goes for all of these lots."

On a day when the principal dealers in the field were otherwise occupied, no telephones were booked and the cup sold to a private collector from Somerset at £50,000 (plus 19.5 per cent buyer's premium).

He left the room swiftly after purchasing the cup and a preceding lot, a 2 3/4in (7cm) diameter "Hellenistic" gold mount, repoussé decorated with a bearded male figure. Again, it sold at the lower end of a £1000-2000 estimate.

A gold spoon with a fluted oval bowl centered by a profile portrait bust and a stem decorated with lions pursuing an antelope sold to a commission bidder at its low estimate of £5000. No date was given for the spoon but the catalogue ventured the design was "redolent of Roman imperial metalwork emanating from the Eastern Mediterranean, or North Africa".

Following the sale, Mr Schwinge told ATG: "We had prepared ourselves for the gold not to sell in light of the differing opinions cast before the sale, but we decided to leave it to the market to decide and are delighted that the items sold."