Copper-alloy gilt Roman coin mounted on iron object

Large brass of Nero, diameter 3.4cm. Gilded.Obv. Head of Nero r., laureate, within inscription IMP NERO CLAVDIUS CAESAR AVG GERM... Rev. Rome on heap of armour, holding in right hand a victoriola, and in left a spear. In exergue, ROMA figure flanked by letters S C. Border of billets. 3 perforation in edge. Found stuck to an iron object thought to be part of a horse-bit. Worn.Probably instrusive – B.B.