The Webley Mark II is a historic top-break, self-extracting service revolver adopted by the British military in 1897. Chambered for the heavy-hitting .455 Webley cartridge, it featured a modernized shorter smokeless-powder cylinder than its predecessor. It saw extensive use in the late 19th and early 20th centuries. 
 
Historical Overview
Adoption: The Mk II replaced the original Mark I. The primary modification was a hardened steel frame, a modified cylinder cam, and a rounded "bird's head" butt shape.
Cartridge: The .455 Mark II cartridge was loaded with cordite instead of black powder. It typically pushed a 265-grain lead bullet at roughly  to achieve  to  of energy.
Legacy: It was a reliable, fast-reloading sidearm that eventually led to later variations like the famous Mark VI. 
 
Important Collector & Shooter Notes
Cylinder Modifications: Many Mark IIs imported to the US after WWII had their cylinders "shaved" or modified to fire the cheaper, more widely available  cartridge using moon clips. This alteration typically lowers collector value.
Ammunition Safety: If you own an original, you should exercise extreme caution with modern  ammunition. Original Webley revolvers were designed for lower pressures (around ) and modern  or .45\text{ Auto Rim loads can severely damage the frame.
Finding Ammo: Modern factory  ammunition is manufactured by brands like Fiocchi and Hornady, making it feasible to shoot if you track it down. Many enthusiasts opt for handloading with mild smokeless or black powder substitutes. 
Firearm purchases require a background check and must be picked up in person by the purchaser
SBR transfers will not be accepted