This is a particular interest of mine. I WW2 and since, there have been many ingeneous solutions for hiding firearms. I have seen single shot pistols hidden in lipsticks, pencils and even a couple in cigarettes! These are fired by pulling a string with your teeth! Not suprisingly they were very dangerous for the user. I have even seen a 5 shot pistol in the form of a ring! It is little larger than one of standard size!
Amazing.