They are clad, not plated.
Pres/ Native American $1
Composition consists of a core of pure copper with an outer layer of manganese brass consisting of 77% copper, 12% zinc, 7% manganese and 4% nickel.
Including both the core and outer layers, the overall composition is 88.5% copper, 6% zinc, 3.5% manganese, and 2% nickel.
Diameter = 26.5 mm and weight = 8.1 g
Missing one clad layer weight approximately 5.8 g - 6.1 g
Suggest checking by weighing your coins.