Webley .455
 
This example of the Webley .455 comes with the open-topped holster for use with the P08 web equipment. The pattern of holster was favored by Machine Gun units and the Royal Flying Corps. Anyone who has fired a .455, can tell you that it will stop a charging Rhino. It is a BIG bullet.
 
A close-up of the "Webley Mark V patent 1919" markings on the revolver.