I know that OMS error [Off metal Strike] is when the sheet metal used to blank coins for a particular denomination are put into other.
For example an SS metal normally used for Indian Rs 1 is put into a Blanking press for Rs 2 [the intended metal being Cu-Ni] and these coins are then struck with a Rs 2 die. Thus these coins become OMS.
The other case is a normal Rs 1 planchet that by error enters into the press meant for striking Rs 2 coins ... these become the "Struck on Wrong Planchet" errors
What would be error type be when a metal in this case Cu-Ni is the right metal for Rs 2, was put into a blanking machine of size for Rs 1, the coins were struck correctly with Rs 2 denomination.