An unknown number of guns are being built with the mechanisms, causing problems for the police and ATF officials. Photo: An ATF agent holds a generic unfinished receiver, back, and one that has been manufactured, front, at an ATF field office in Washington, on May 06, 2014. The ATF is trying to crack down on the trade in the makeshift guns by targeting shops and individuals who offer to turn the unfinished receivers into functional pieces for firearms. (Photo by Bill O'Leary/The Washington Post)

A 19th century bicycle safety lock is displayed in an old frame in the Museum of Domenico Agostinelli in Dragona, near Rome October 30, 2014Italian collector Domenico Agostinelli, 74, has a passion that has led him over the past 60 years to pick up and collect things of all types, from antique art to everyday objects of the past and present. His collection includes a 65-million-year-old dinosaur egg, meteor fragments, a car that once belonged to American mob boss Al Capone, a lock of hair of Italian national hero Giuseppe Garibaldi, toys, weapons, musical instruments of all kinds and many more. (Photo by Tony Gentile/Reuters)

Floating on clear deep water and reflections near the cave entrance. Visitors can either bring their own kayaks or rent boats from the local community to paddle deep inside the cave and marvel at its wonders on March 2015 at Tham Khoun Ex, Laos. Tham Khoun Xe, commonly known as the Xe Bang Fai River Cave, in Laos, has over 15km of passages filled with awe-inspiring views and wide expanses of water. Photographer, John Spies, 59, captured scenes from the entrances of the huge underground river passages, intricate cave formations and views from a passage high above the water. The cave is formed by the Xe Bang Fai river, a major tributary of the Mekong and in the dry season can be traversed using inflatable kayaks. (Photo by John Spies/Barcroft Media/ABACAPress)

Iranians flash the victory sign from their car while celebrating on a street in northern Tehran, Iran, Thursday, April 2, 2015, after Iran's nuclear agreement with world powers in Lausanne, Switzerland. The United States, Iran and five other world powers on Thursday announced an understanding outlining limits on Iran's nuclear program so it cannot lead to atomic weapons, directing negotiators toward achieving a comprehensive agreement within three months. (Photo by Ebrahim Noroozi/AP Photo)

“Pantsir-S1 (NATO reporting name SA-22 Greyhound) is a combined short to medium range surface-to-air missile and anti-aircraft artillery weapon system produced by KBP of Tula, Russia. The system is a further development of SA-19/SA-N-11 and represents the latest air defence technology by using phased-array radars for both target acquisition and tracking”. – Wikipedia

Photo: Test of the surface-to-air missile Pantsir-S rocket and gun system in the conditions of the Polar region on the range “Pemba” near Vorkuta, approximately on October 20 2012. According to the statement of military, during doctrines five cruise missiles from five were destroyed. (Photo by Alexey Reznichenko)

People pause at a memorial set up for victims of a mass shooting in Las Vegas, Nev., on Tuesday, October 3, 2017. A gunman opened fire on an outdoor music concert on Sunday. It was the deadliest mass shooting in modern U.S. history, with dozens of people killed and hundreds injured, some by gunfire, some during the chaotic escape. (Photo by John Locher/AP Photo)

A Colombian flower grower selects a rose for a bouquet ahead of Valentine's Day in Subachoque, February 2, 2015. Colombia is the world's second-largest flower exporter behind the Netherlands. The Andean country exports around 500 million flowers to the U.S. for Valentine's Day, according to the Colombia Flower Growers Association. (Photo by John Vizcaino/Reuters)

Two young women pose for a portrait, dressed in robes after collecting their Bachelor degrees in Conakry on October 12, 2020. Presidential elections are to be held on October 18, with incumbent President bidding for a third term in office, defying critics who say he forced through a new constitution this year enabling him to sidestep two-term presidential limits. (Photo by John Wessels/AFP Photo)