File:Common Seal of Corporation of Dublin (1230).png

1230 Common Seal of the Corporation of Dublin. Circumscribed in Latin: Sigillum Commune Civium Dublinia(e) ("Common Seal of the Citizens of Dublin"). Depicting the gateway of Dublin Castle as an heraldic Tower triple-towered. "The Three Castles have been the symbol of Dublin since 1230, when they first appeared on a city seal as three towers situated around one of the fortified gates of the city" (Michael English, The Three Castles of Dublin: An Eclectic History of Dublin Through the Evolution of the City's Coat of Arms). Described as follows by Seán Duffy:

• “The citizens, desiring to portray an image of this city of which they were so proud, to capture the essence of it, chose to display to all a heavily fortified castle, high towers, high stone curtain walls, parapets guarded with buglers and crossbowmen, and a gateway blocked by a sentry bedecked in armour and weaponry. These are images that portray strength, wealth, status, to be sure, but they suggest also perhaps a sense of insecurity. This image is, for all the world, that of a city under siege. The watchmen on the keep are sounding the alarm, as are the sentries on the walls; on the two gate-towers the archers stand poised with their crossbows, and no-one is likely to get past the guard on the doorway: the heads of those who tried are impaled above. They are it would seem, Irish men, Irish rebels, the city’s enemies. The message of the Common Seal is that Dublin is the proud capital of a colonial enclave; it is surrounded by enemies; and it must provide for its own defence. Hence its walls, towers and fortified gateway.” (Seán Duffy, ‘Ireland’s Hastings: The Anglo-Norman Conquest of Dublin’, Anglo-Norman Studies XX) (Quoted in [1])