1942 Three Pence. Is This A Different Metal Than Normal?

From the pitted surface it is clear that the coin has suffered corrosion. It probably has been stored in an aggressive (chemical) environmont. It ould also have been buried for a long time. A corrosive environment causes changes of coulor because of the removal of one of the constituent components from the surface. The composition of these 3d coins is (1937-1970) Nickel-brass (79% Cu, 20% Zn, and 1% Ni). The component dissolved usually is zink (Zn). This will change the colour of the coin to red. Of course other reactions with the metal different coulours could result.