Butting bull series.     AR Denarius, c. 206-195 BC.   Obv.    Helmeted head of Roma right; behind, X.        Rev.   The Dioscuri galloping right; below horses, bull butting right; in exergue, ROMA.     Cr. 116/1b.     3.01 g.   18.50 mm.      R.  Rare. Somewhat porous, bright and lightly toned.    VF.     Rare.