I am not sure about the tinctures on this shield.  This is why a blazon is important.

http://upload.wikimedia.org/wikipedia/en/1/13/Philadelphia_City_Seal_Color.jpghttp://www.philaplanning.org/graphics/cityseal.gifhttp://www.instoneinc.com/gallery/Seal_of_Philadelphia.jpghttp://www.flagshag.com/philadelphiacityseal.gif

Answered my own question: ... the emblazonments are bogus.

http://www.phila.gov/philacode/html/_data/title21/chapter_21_100_city_emblems_co/21_101_the_city_seal_.html

Compare the blazon below to the seal here: http://www.phila.gov/

<hr class=“bbcode_rule” >

ARMS—On a blue field, a fess golden between a plough above and a ship in full sail below; both proper.

CREST—A right arm, nude, embowed, couped at shoulder, holding a pair of scales; all proper.

SUPPORTERS—Two females, standing full face, the one on the right side of the shield habited white and purple, crowned with an olive wreath; in her right hand a scroll, charged with an anchor; all proper; the one on the left side habited white and blue; in her left hand a cornucopia, proper.

MOTTO—PHILADELPHIA MANETO.

(2) The seal of the Mayor of the City shall contain the words and letters on a riband, like the first seal adopted by the corporation—Seal of the City of Philadelphia—and shall have a diameter of 2&#188; inches.

Michael Swanson wrote:

ARMS—On a blue field, a fess golden between a plough above and a ship in full sail below; both proper.

Other than the semicolon (I would have used a comma), this is a good example of what I would call moderately modernized blazoning.  The only other thought would be "golden fess" instead of "fess golden," but who, other than the people preparing the web graphics cited by Mike, could not properly emblazon these arms from the blazon?

Here are some good examples of a city proudly displaying its arms, from city hall to dumptruck.

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Here is a nice relief of the Philly arms ....

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Again AWESOME!