The Medusa Model 47
http://www.kitsune.addr.com/Firearms...a_Model_47.htm
An excerpt:
"The Medusa is a very unusual revolver produced by Phillips & Rodgers that have the ability to chamber multiple calibers in the same revolver. The Medusa chambers, fires, and extracts 25 different cartridges in the .38/9mm/.357 ammunition range. The obvious advantage of this is that the person can use the revolver for targeting shooting with a lighter and less expensive caliber and switch to a heavier caliber for self defense."