The 4"/50 (10.2 cm) BL Mark VII was a secondary armament mounted on Orion-class and other capital ships of the era.
Naveaps.com entryWikipedia entryEscutcheon ship
Escutcheon
noun
1.
a shield or shieldlike surface on which a coat of arms is depicted.
2.
an ornamental or protective plate around a keyhole, door handle, drawer pull, light switch, etc.
3.
Nautical. a panel on the stern of a vessel bearing its name and port of registry.
Outer sideRudderInner Side