Now here is one I am sure you haven't seen before.
Chicago City Alderman Star shaped bumper badge circa 1920-30‘s. This badge was made to be mounted above the license plate on an alderman’s private car so that the car could cross police lines and park anywhere without getting towed. This type of badge, which was most often used by sheriff’s department officers, is considered scarce and very hard to find by badge collectors. An aldermanic version of this type of badge is virtually unheard of and must be very rare indeed. This badge is made of nickel or chrome plated cast bronze, weighs 10.5 ounces and is 5 inches across. The convex center features the Chicago city coat of arms with the words “CITY OF CHICAGO” at the top and “ALDERMAN” at the bottom. The center of this badge is worn so I don’t know if this badge was plated when issued or plated later.
For more scans go to http://www.ecrater.com/product.php?pid=2873255