A rare watch camera made in Birmingham in the 19th century has been discovered and is going on sale at auction next month.

The Lancaster Ladies Watch Camera is expected to fetch between £10,000 and £15,000 when it goes under the hammer in Knowle on May 9.

Auctioneers Bonhams said the watch was brought into them by a gentleman whose grandfather had owned it originally.

He was a cabinetmaker at the Birmingham-based firm, J. Lancaster & Son, probably working on the many wooden cameras sold by the company.

The vendor noticed that among his collection was what looked like an ordinary nickel-plated pocket watch case when closed.

Lionel Hughes, Bonhams: "This is a truly exceptional piece."

However, when he opened it he discovered that it actually contained a tiny camera inside.

Lionel Hughes, Bonhams' camera specialist, said he was delighted to come across the item.

"This is a truly exceptional piece," he explained. "The Lancaster Watch Camera was patented in October 1886 and made until 1890.

"Such tiny cameras were the forerunners for the 'spy' camera - a mechanism disguised as a different object.

"However, it would have been very inconvenient to use as four very small catches had to be released in order to remove the glass screen and to fit a separate metal sensitised material holder for each exposure.

"As a result, the model sadly sold badly and is much rarer than the improved version which came on the market in 1890.

"The ladies' pattern is therefore particularly special, and only four original models are known to exist.

"The holders are also very rare. A model sold at auction in 1992 for $47,500 so we have great hopes for our sale in May."