Key type stamp

An unused Trinidad key type stamp showing Britannia
A used German key type stamp for Togo
An 1892 4c stamp for Ivory Coast (Côte d'Ivoire) of the Navigation & Commerce key type series
These mint British stamps for use in Ceylon exemplify the key plate approach.

Key type stamps are stamps of a uniform design that were widely used by colonial territories in the 19th and 20th centuries.