At The Firearm Blog – apparently, the Germans weren’t happy with suppressed HK pistols, and someone had to go and figure out a system to effectively suppress a S&W 625 revolver, in .45 ACP. The system is actually quite ingenious, as the cylinder gap is covered by a plate that swings out to allow access to the cylinder for reloading, but during firing is closed and prevents a significant amount of noise from escaping the cylinder.
Oh those crazy Germans.