ONE of rail history's most mysterious treasures was the star of thousands of models on show at the weekend.

Only 30cm high, the 200-year-old brass and copper Sans Pareil is one of the oldest model steam locomotives in the world.

Experts think it could be the missing link between early railway engineering and all modern engines.

It was loaned by the National Railway Museum, in York, for a two-day Model Mania show at Locomotion: the National Railway Museum at Shildon, County Durham, where its history was outlined to some of the 4,000 visitors.

Too delicate to be handled without gloves, Sans Pareil, which means Without Equal, shares the same name as the locomotive most associated with the Shildon museum, the steam engine built by Timothy Hackworth for the Rainhill Trials in 1829.

The model was originally thought to have been one of Hackworth's prototypes, but now experts at Shildon believe it is much older and may have been designed in about 1802 by earlier pioneer Richard Trevithick to test engineering concepts.

Anthony Coulis, curator of the Shildon museum, said: "It really is priceless. He was experimenting whether he could made a steam engine using two cylinders, and so it is a forerunner of virtually every modern engine in the world."

Model Mania was organised by volunteer Graham Eason and attracted exhibitors from all over the country, including the Southdown Railway Company, which ran a Continental steam layout. Trains, boats, planes, fairground rides, forts and castles, dolls houses and gipsy caravans were all on show and there were displays by North-East model clubs as well as major companies such as Airfix, Hornby, Corgi, Bachmann and Games Workshop.

Museum manager George Muirhead said: "This is one of our biggest events of the year. It is really popular with children and model enthusiasts."