Moris Sadioglu, a Turkish collector, is coming to London next week armed with what he believes is evidence that the gilded copper tombak helmet, decorated with leaf-shaped motifs, was made 'now'. He has the backing, he said, of several experts in Britain and Turkey, including the Islamic and Military museums in Istanbul, as well as technical data.
Scientists at Oxford University deduced that from 'the total lack of corrosion and the clean appearance of the mercury gilding, the evidence points very strongly to the conclusion that the piece is recent'.
According to Sabah-Aktuel, a leading Turkish newspaper, the helmet is one of eight 'dubious' pieces that have found their way on to the market. Among them are two 16th-century chanfrons, or horse armour, and another helmet, which were withdrawn from last month's auction at Sotheby's. Sabah has tracked down two of several forgers that it believes are working in Turkey, specialising in jewellery and copper.
Robert Elgood, who was Sotheby's consultant on Islamic arms and armour for four years in the 1980s, said that he had warned the auction house, in an unofficial capacity, at the time of the sale that the helmet was 'quite clearly fake'. He said that there were 'a dozen reasons' why the piece was wrong: for example, the peak on the front was 'totally unIslamic, concave in shape, which it shouldn't be . . . It looks more like a baseball cap. The person who has designed it hasn't understood the . . . discipline in which he's working'.
Brendan Lynch, co-director of Sotheby's Islamic and Indian art department, said: 'If someone believes something is fake, and it's within the five-year guarantee period, and they can produce evidence, we guarantee their money back.'
At the time, it was authenticated by a leading expert at the Victoria and Albert Museum - in fact, because it showed little sign of age, they started from the premise that it was a fake.
As John Carswell, co-director of that Sotheby's department, pointed out, expert opinion in the academic world was so often divided.
Neither was scientific testing always conclusive, Joe Och, Sotheby's company secretary, said. Another 16th- to 17th-century piece that underwent two separate metallurgical analyses 'had completely different results . . . differing by several centuries . . . It is not so much the analysis as the interpretation that makes a difference.'
What particularly upsets Mr Sadioglu, who has been a regular at Sotheby's Islamic art sales for many years, is that on his way back to Istanbul, just after the sale, he heard a rumour that his piece was fake. He contacted Sotheby's, insisting on a letter confirming its authenticity before paying. He said that Sotheby's took three months to respond, and that they charged interest for that period - which he said amounted to pounds 1,800 - which he wants returned.
However, Mr Och said that refunds do not include the interest or fluctuations of currencies: 'If he hadn't paid after the sale, he would have been charged interest as the main contract is between him and the seller.'