At the RKO Cinema Theatre , Leicester Square , London , a collection of American gangster weapons is on display . A collection of the most modern revolvers - those of the bigger type are used by the police but the racketeers favour the smaller weapon . The particular one that is used mostly by gangsters is the double barrelled Derringer , which is being held by the girl . This is usually carried in the waistcoat pocket but should the racketeer wish to carry a larger gun it is invariably carried in a holster under the left arm pit . 21 October 1931