Coat of Arms has been painted by Nick Walker on 71a Park Street - Bristol (England).
(Click on the photo to see a larger version)
... above Vincenzo's Pizza Place.
This is not a Banksy… but a piece of graffiti art by Nick Walker, another famous Bristolian. Walker started in the 80's and was actually one of the people who inspired Banksy. You can find more information about this artist on his website.