Two new options for the back of the coin.
Left: The sword, scale and blindfold from the Cities Insignia. This could be nice having a since of location and history (city hall/1870) on one side and iconic symbolism that depicts values of the other. The blindfold could even have an inscription similar to the Latin on the City Logo "Justitia Virtutum Regina".
Right: Another well recognizable icon of Columbia are the clocks on Main St. The clocks might not have as much "meaning" as the sword and scales but does have history that helps define the areas history, is in close proximity to city hall (which could compliment the front of the coin) and, design-wise, would translate well and look nice on the coin.