The painting is the last thing on the coin... so this could not be plated afterwards very easily. These coins were struck on nickel-plated steel, so it is very unlikely to be toning.
It actually looks legit. I suspect it could be a brass-plated steel planchet - the 2010 lenticular dinosaurs and holiday coins were struck on similar sized brass-plated steel planchets. An XRF would be immensely helpful...