There’s a great article that I recently ran across over at the blog Manhattan Unlocked: The Unbelievably Rich and Inordinate History of Manhattan. The specific post was uploaded on December 5, 2010, and is entitled “Decoding the Seals of the City of New York.” It’s a great article, profusely illustrated, and gives the history of the current seal of the City as well as its long history and the changes (and errors) that have been made to it over the years.
The coat of arms, centrally placed on the seal, might be blazoned (they were never officially granted by any granting body of heralds) as: Argent the sails of a windmill set salitirewise between in pale two beavers statant and in fess two flour barrels proper. (Though a Civil War era banner containing the arms has the field Azure (blue) and the charges Argent (white or silver). And I’ve seen renditions where the field is Or, yellow or gold.) One depiction of the arms may be found on the Heraldry of the World website at: http://www.ngw.nl/int/usa/newyork.htm
I highly recommend that if you are at all interested in the meaning of the elements or in the history of the coat of arms and seal of what is probably the epitome of the American city, that you take the time to read this article. It can be found on-line at: http://manhattanunlocked.blogspot.com/2010/11/architecture-lesson-1.html