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Our original design had a snapping motion from a Geneva mechanism and several springs. However, this upward snapping motion had to be pretty powerful as the portion that needs the most torque is the last portion of the snap. This led to the coin being "thrown up" back out of the mouth. While we We could have designed around this problem, either by fine-tuning the tongues action to throw the coin backwards on the upward journey, by having an upper jaw that would direct the coin back into the throat, or having a more clip-in like interface for the coin to be slid into instead of just on top of the tongue.