Banner of arms of Castlebar in Ireland. It was granted on the 20th of August in 1953. 

(Note: This representation is based upon an entry in the Flags of the World website/mailing list (FOTW) which, per WP:RSP#Flags of the World has (since 2011) not been considered a reliable source on the English language Wikipedia. See also: this discussion.)
Own work; reconstructed from https://www.crwflags.com/fotw/flags/ie-may.html#castlebar
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