A method and system for prevention of dust accumulation on a coin sensor assembly (67) in a coin handling machine (60), includes a lower optical element (83, 90) positioned below a coin track (63) and then either, or both of, 1) blowing off dust that tends to accumulate on the cover (83) for the lower optical element (90) and 2) coating the cover (83) for the lower optical element (90) with a transparent conductive coating (83a) that is electrically grounded to prevent accumulation of dust due to static electrical attraction. A fan unit (82) is positioned adjacent the cover (83) for blowing dust off the cover (83) during operation of the coin handling machine (60). The method and system is preferably a optical reflector system with an upper optical element in the form of a reflector (86, 87) and a transparent conductive coating of material (87a) is also provided on the reflector (86, 87).