A block of 19th-century Hong Kong postage stamps featuring Queen Victoria’s head sold for a record €601,000 in the former British colony, organisers said.

The set of four olive-coloured stamps was described as “extremely rare” with organisers chalking up their unusual colour – they should have been a brownish-grey tone – to a printing error.

The pre-sale estimate had been as high as €1.1 million, but it was still the highest price ever paid in the southern Chinese territory for a single lot of Hong Kong stamps. They went to an anonymous buyer.

The face value of each of the stamps, which were issued in 1865, was 96 Hong Kong cents (12 US cents at current conversion rates).

The stamp and banknote sale by auction house Spink capped off a busy weekend of auctions in Hong Kong, with British composer Andrew Lloyd Webber’s wine collection fetching a higher-than-expected €4.1 million at Sotheby’s.

Another wine auction raised about €8 million, well above the €6 million organisers had predicted.

“We are excited to see strong participation by Hong Kong, mainland Chinese and our Asian clients, along with numerous bidders back in America participating as well,” said John Kapon, chief executive of auctioneer Acker Merrall & Condit, which organised that sale.

The city was returned to Beijing by colonial power Britain in 1997, but maintains a semi-autonomous status within China.