George "Machine Gun" Kelly is probably considered one of the most famous "gangsters" from the prohibition era. "Machine Gun" was born George Kelly Barnes on July 18, 1895, to a wealthy family living in Memphis, Tennessee. His nickname came from his favorite weapon, a Thompson submachine gun. Kelly’s most famous crime was the kidnapping of oil tycoon & businessman Charles Urschel in July 1933 for which he, and his gang, earned 200,000 dollars ransom.
The United States Thompson submachine gun (Tommy Gun) was one of the most used guns by the US during World War II, used by many nations like Britain and Canada much like most American guns. In this picture you have two different mags, the most common on the left and the barrel one on the right which contains more ammo.
From Gangland to the Battlefield - 15 Amazing Facts About the Thompson Submachine Gun - http://www.warhistoryonline.com/war-articles/gangland-battlefield-15-amazing-facts-thompson-submachine-gun-%e2%9e%94.html
Winston Churchill squints as he test fires an American M1928 Thompson submachine gun, many of which were supplied to England under the Lend-Lease program. Note the unusual hybrid forestock with both descending pistol and horizontal hand grips.