The .38 Whitney revolver that Lewis Powell brought into the Secretary of State’s house. The gun broke when Powell brought it down onto Frederick Seward’s head.
Image Source: LOC
Lewis Powell’s Whitney Revolver
The History Behind Lincoln's Assassination
LincolnConspirators.com 
Can anyone tell me the serial number of Lewis Powell’s Whitney pistol? I can’t find it listed anywhere.
The serial number of Powell’s Whitney is 1011.