The 1943-S "Goiter" is a most unusual variety in the Washington Quarter Dollar series. For some reason, the obverse die sank at the junction of Washington's jaw and throat, causing a raised, goiter-like bulge (a goiter is swelling on a person's neck caused by an enlarged thyroid gland). In this case, the bulge is so severe that it actually distorted the shape of parts of the legend IN GOD WE TRUST; the word WE and the letters UST now lean left.
According to the PCGS CoinFacts Condition Census, MS65 is the finest grade available to collectors.