The FBI’s reference firearms collection contains more than 7,000 guns—just about every make and model, from John Dillinger’s Prohibition-era revolver to the modern battlefield’s M16 and almost everything in between, including examples of all the sidearms special agents have carried over the years (shown above is the Colt Police Positive .38 Special revolver that agents were armed with in the 1930s). But, as the FBI’s firearms examiners will tell you, the single most important piece is the one that helps investigators close a case on any given day. For more information, see: http://www.fbi.gov/news/stories/2013/april/fbi-gun-collection-firearms-that-help-solve-crimes