THIEVES have stolen a brass nameplate from an historic locomotive while it was on display at York's National Railway Museum.

The plate, which is oval-shaped and painted black, was taken from the Furness Railway 0-4-0 No 3, a steam locomotive built in 1846.

Nicknamed Coppernob, because it has a copper dome over the fire box at the end of the boiler, the historic engine is on display in the museum's Station Hall.

The theft was discovered by staff during routine cleaning on January 2 and was reported to the police.

Andrew Scott, head of the National Railway Museum, said: "Unlike many museums where artefacts are exhibited behind glass, these great railway treasures are openly displayed in good faith for the benefit of the thousands of visitors who come to the NRM to enjoy with our collections at close quarters.

"It is a very great shame when that trust is abused by a small minority of extremely selfish and dishonest people.

"The plate taken from Coppernob is priceless to the nation but worth much less on the open market because it can never be sold or displayed honestly.

"Fortunately theft of items on display is rare and the NRM has an excellent track record over its 31-year history. Nevertheless we will, as a matter of course, review our security arrangements following this incident."

The nameplate is the latest in a string of thefts of railway heritage. Experts believe they are being melted down and sold.

A nameplate was stolen from the steam locomotive Dame Vera Lynn - which is featured on ITV's Heartbeat - while it was being repaired at an engineering workshop in Bury, and West Yorkshire Police are appealing for information after the "totem" signs from Damems station on the Keighley and Worth Valley Railway were stolen.

Lincolnshire Police are investigating after brass castings and fittings were taken from the Jurassic locomotive on the Lincolnshire Coast Light Railway.

Coppernob was used to pull loads of iron ore and slate from North Cumbria and was last used in 1898.

It also hauled the first passenger train on the Furness Railway and was placed in a glass case at Barrow railway station on its retirement.

It was removed during the Second World War after the station was bombed but returned home to the Furness area to mark the 150th anniversary of its first passenger service in 1996.

The locomotive was designed by Edward Bury, the rolling stock manager of the London and Birmingham Railway and Great Northern Railway.

It was built by Bury, Curtis and Kennedy for the Furness Railway and was the company's third locomotive.

Anyone with information about the theft is asked to phone York Police on 0845 60 60 247.