The limited Mark IX coastal-defence model preceded the Mark X, which introduced a revised breech and rifling. The Mark X remained in British coastal service until 1956 and in Portuguese service until 1998, while surviving examples illustrate its wide distribution. Vickers built 284 guns, and the type armed Cressy, Drake, Duke of Edinburgh, Warrior, King Edward VII, and M15-class vessels. The less successful long-barrel Mark XI provides a contrast: a gun's reputation depended partly on whether enough suitable ships carried it long enough to develop effective service experience.
Notable Point · 15:11-18:18
The long service life of the 9.2-inch gun
The Mark X 9.2-inch gun connected armoured-cruiser firepower with coastal defence, later monitors, and an unusually long international service life.