When the producers of "Fury" planned to make a technically correct film about an American World War II tank crew’s exploits, they ran into a problem. The type of tank they wanted to use was nowhere to be found, the result of heavy casualties on the battlefield.

So they had to use the wrong tank.

And that’s a problem that a lot of collectors, or rather would-be collectors, of certain World War militaria can encounter. Many of the most desirable collectibles, like early tanks, airplanes and certain armaments, no longer exist except in photographs, old newsreels and the occasional museum.

In fact, when trying to find an original Voisin airplane, which had become the world’s most common type of aircraft in the years leading up to World War I, one noted collector, Peter Mullin, found there were none left.

“I searched the world,” Mullin recalled. “I found one, in Switzerland, but it turned out to be a replica.”

The Smithsonian’s National Air and Space Museum in Washington, D.C., claims to have the oldest surviving Voisin bomber, a Type 8 manufactured in 1916.

“Tens of thousands of Voisin airplanes were manufactured,” Mullin said. “It seems almost unimaginable that they’re all gone.”

The same could be said about certain early models of the once-ubiquitous Sherman tank, which were also manufactured in the tens of thousands.

In "Fury", the 2014 film starring Brad Pitt and Shia LaBeouf, a five-man crew in the storied 66th Armored Regiment, part of the U.S. Army’s 2ndArmored Division, pushes into the heart of Germany in April 1945 – just days before the Nazi surrender.

In the film’s telling, the crew was really attached to this particular tank – enough to bestow the name "Fury" on it – and they’d been fighting together in it since the North Africa campaign in 1942. With that provenance, "Fury" likely would have been a Sherman M2 or M4A3, each of which went into production in 1942. But here’s the rub: It would have been unlikely for an early-model M2 or M4 to have survived all that time. Tank battles in that part of the war, you see, had a 50 percent casualty rate.

In fact, only one Sherman tank – a Canadian one – is known to have survived all the way from the D-Day landing in June 1944 to V-E Day in May 1945. One!

So the filmmakers used a later model, which went into production in late 1944. A number of those examples still exist, as they were produced through the Korean War and even later. Those enjoyed a better survival rate, if for no other reason than they were no longer up against the German juggernauts.

The American Sherman tanks in the movie – 10 were used – all came from the Tank Museum in Bovington, in southern England, which boasts one of the finest and most complete collections of historic tanks.

That’s also where the filmmakers got the movie’s nearly indestructible German Tiger I tank, known as a Panzer, a relic whose production ended with the demise of the Third Reich. The Panzer at the Tank Museum is reputed to be the only surviving Tiger 131 tank still in working order.

That brings up another obstacle facing would-be American collectors who might want a World War II tank: The few that exist are generally “over there.” They were seldom judged to be worth the trouble to ship back to the U.S.

“I heard of a guy in Texas who was supposed to be building an exact replica of a Tiger I,” said Leigh Miller, a collector of tank memorabilia and an authority on tank trivia. “But I’ll believe that when I see it.”

There’s another interesting aspect of appeal for military vehicles like the Sherman tank. Production notes from "Fury" mention that that tank was “designed and built by Henry Ford,” while the German tanks were masterminded by Ferdinand Porsche. In truth, Ford Motor Company didn’t design the Sherman, but it did build a small number of them. General Motors and Chrysler built the vast majority.

Regardless of who built them, a key reason why so few Shermans have survived is that the early models had a reputation for being death traps. British soldiers called them Ronsons – like the lighter – for how easily they burst into flame.