West Auckland Historical Society have been very fortunate in obtaining the coat of arms used by Waitakere City from 1989-2010.
They're on prominent display in the dining room at Mill Cottage, on Sel Peacock Drive, Henderson. Trevor Pollard, WAHS President, is pictured (I said, come on Trevor, let's have you beside them!)
They were originally the arms for the Waitemata County Council, originally a spread-out territorial authority dating from 1876 which included all of West Auckland, North-west Auckland up to Helensville and Silverdale, and the North Shore. Gradually, town districts and boroughs chipped away at the district, becoming independent bodies, until by 1973 all that was left was a county focussed almost entirely on West Auckland with prominent exceptions such as New Lynn, Glen Eden, Henderson, and land owned by Auckland City (Waikumete Cemetery) and the Auckland Regional Authority (parks out in the Waitakeres). A year after the arms were granted to the county, it reformed into Waitemata City, which became Waitakere City in 1989 on amalgamation and mop up of the former independent areas which had broken free from the old county from 1910.
Some other Auckland area arms:
Auckland City's coat of arms dates from 1911.
Manukau City's arms (granted 1968) probably date back, like Waitakere, to the county council days.
Birkenhead, from 1973.
Takapuna, from 1954.