A vintage sterling silver Violin Case charm that opens to show a machine gun inside, just like the fabled weapons supposedly carried by American gangsters during the 1920s and 1930s.  
 
Of course in real life this may not actually have happened, however the Thompson machine gun (colloquially called Chicago typewriter) was apparently carried in a similarly-shaped case, hence the origins of the belief.
 
This charm is unmarked and tests as silver. It is in very good condition, with a good, secure closure.  
Comes with a jump ring ready to attach to your bracelet.