Model trains capture the sweep of American economic history, keeping alive railway company names such as Erie Lackawanna, Western Maryland, and Lehigh Valley, that were long ago caught up in consolidation.

That historical dimension turns many railroad buffs into sticklers for accuracy, evident Sunday at Greenberg's Great Train & Toy Show at the Greater Philadelphia Expo Center in Oaks.

"Pennsylvania Railroad never ran that engine," said collector Joe Desiata, pointing at a 1930s model steam engine that was actually used by the New York Central Railroad.

"Manufacturers make an attempt to appeal to a broader base of customers" by taking the liberty of putting the Pennsylvania Railroad label on an engine used by its rival to the north, Desiata said.

Three or four visitors pointed out the historical incongruity, said Desiata, 55, of East Fallowfield Township.

He is trying to empty closets by selling some of the collection he has built up since he was 7, but he's not necessarily trying to make a profit. That's not popular with full-time dealers who are trying to make a living, he said.

His asking price for the faux Pennsylvania Railroad engine was $100, even though he paid $160.

Sales were good on Saturday, when about 1,500 people visited, but slower on Sunday, Desiata said.

Dealers occupied about two-thirds of the space; the rest was used for displays of eight local clubs.

One of them, Allegheny Western Lines, is not based on a real historical railway company, but rather fashions the past in its own fictional history.

That history holds that three foundering railroads - the Erie Southern, Penn Northern, and South Penn - were merged in the early 1950s to form Allegheny Western, said Chris O'Brien, a founding member of the club based in Fort Washington.

In reality, such mergers were common in the 20th century.

Allegheny Western Lines is a modular group, which means its members build 2-by-2-foot sections of railroad layouts - as opposed to full layouts - that can be combined with those of other clubs, such as the Royersford Modular Model Railroaders, which was also at the show.

"The goal is to create a model that can be photographed and you can't tell if it's a photo or real," O'Brien said.

O'Brien, 41, is partial to trains from the 1930s and '40s, and he strives to be true to that period. "When you select an era, you try to model that era," he said.

Nevertheless, O'Brien, of Northeast Philadelphia, happily tolerated his son, Tyler, inserting a modern hopper car into a train pulled by a 1930s-era Pennsylvania Railroad M1 engine.

Model trains offer a tie not just between fathers and sons, but also between grandfathers and grandsons.

Jay Beraton, 69, of Northeast Philadelphia, said his 14-year-old grandson, Noah, was running his set from 1952.

In the Hartman family of Roslyn, Aidan, 3, drives the interest in trains. "We're learning a lot through him," said Aidan's mother, Jessica Hartman.

Aidan, wearing a Thomas the Tank Engine T-shirt, has prompted multiple visits to the Strasburg Rail Road in Strasburg, Pa., where Thomas the Tank Engine makes regular appearances.

Though model trains were the focus of the Greenberg show, a slot-car racetrack, where racers were competing for prizes at the end of the day, drew a crowd.

Four-year-old Towen Secoda, with his father, Tim, of Levittown, was clearly fascinated by cars, standing on tiptoe to reach a model 1950s car on the East Penn Traction Club display.

Secoda said he and his son had trains at home but were more interested in slot cars.

"I like them better because you're actually racing them, not just watching them go around," he said.