People have tried to modify or invent firearms for specific tasks for as long as there have been guns. Guns have been made to shoot underwater, to shoot in space, to fit inside every-day object, to be mounted on a glove, to fire tiny rockets. Some ventures proved far more successful than others.

Forgotten Weapons is a great repository of those others. A new vid from Ian McCollum from the vaults of Rock Island Auctions details a Colt Lawman revolver prototype made in the 1970s for Eastern Air Lines. RIA has one of these rare and unusual guns up for auction.

The airline, line many others at the time, had a bit of a hijacking problem. In fact, a rash of airline hijackings spread across the world in the 1970s, which is why it ended up as the plot of many an action movie and thriller in that era.

Most notably, on March 17, 1970, an Eastern Air Lines shuttle flight going from Newark, NJ to Boston was hijacked by John J. Divivo who had smuggled a .38-caliber revolver aboard. He demanded that he be taken to the pilots and then told them to fly east.

When the plane was beginning its descent, Divivo shot co-pilot James Hartley in the chest without warning before shooting the pilot, Capt. Robert Wilbur Jr., in the arm. It’s hypothesized that he was trying to cause a crash.

Despite his fatal wounds, Hartley managed to take Divivo’s gun from him and shoot the hijacker three times before dying. Divivo was still alive and clawed at Wilbur as he attempted to land the plane, still trying to cause a crash. The captain hit Divivo over the head and managed to land the plane safely at Logan International Airport. Incredibly, Divivo survived only to hang himself in jail while awaiting trial.

After another high profile incident in 1972, its no wonder Eastern commissioned Colt to create a handgun the could be carried by their pilots and co-pilots to defend the plane and its passengers. The company elected to take this course instead of buying into the emerging federal Sky Marshal program.

The primary concern Colt had to address was over-penetration. Though it is largely a myth that a bullet hole in the window or fuselage of a plane would cause serious damage or explosive decompression, you can’t imagine tighter quarters than a commercial airline—maybe a submarine. So if a pilot shot a hijacker, the bullet absolutely could not go through him. Likewise, if a bullet were to miss and hit a part of the plane, it had to stop there, period. Kind of a tall order, and Colt’s solution was pretty remarkable.

As Ian lays out in the video above, Colt took a Lawman .357 Magnum revolver and replaced the cylinder with a plastic one that held six steel sleeves. The cylinder was meant to be discarded and replaced after use and each of those sleeves held a bullet made from plaster-of-paris stacked in front of propellant and a primer. The front of each chamber was also sealed to lock out moisture.

To prevent the brittle bullets from shattering when fired or on their way down the barrel, they were housed in a plastic sabot that fell away as soon as it cleared the muzzle.

Of course, the concept only made it to the developmental stage and was never put into production and Eastern Air Lines decided to go along with the Sky Marshal program instead of arming its pilots.

Would a plaster-of-paris bullet that was designed to break apart when it hit pretty much anything do enough damage to put down a hijacker? I guess we’ll never know.

The Sky Marshal Program of the 1970s eventually became a joined effort between the U.S. Customs Service and the FAA. It was started by President Richard Nixon who ordered the immediate deployment of armed federal agents on U.S. commercial aircraft who were, at first, agents from the Treasury Department.

Later, the Customs Service formed the Division of Air Security with the new position of Customs Security Officer (CSO). There were about 1,700 people hired to be CSOs and they were trained at a Treasury complex at Fort Belvoir, Virginia. They were deployed undercover on both domestic and international flights in teams of two and three.

Of course, a lot has happened involving air travel and terrorism since the 70s. Today, the Federal Air Marshal Service handles these duties. The agency is run by the Transportation Security Administration (TSA), which is part of the Department of Homeland Security (DHS), which was created after the terrorist attacks of 9/11.

For a time in the late 1990s and early 2000s, because of the environment in which they work, air marshals had the highest firearms qualification standards in federal law enforcement and they were in the top 1 percent of combat shooters in the world, but the standards were changed when the service was greatly expanded in 2001. On 9/11, there were only 33 active CSOs in the country; by 2013 there were 4,000. For more about the air marshals and their shooting qualification test, go here.