Cheaply made Zinc alloy coins are being passed off as quality. A 2″ coin should never be zinc alloy unless the 3D on either side takes up 70% – 80% of that side, is odd shaped ( in some cases ) or has cut outs ( in some cases .) Ask your vendor what you coins will be based with or centered with. If the tell you Zinc Alloy, ask them why and ask them if your coins can be centered with brass.
The weight of a zinc alloy 2″ 3.5mm thick coin without any cut outs is approx. 45g.
The weight of a brass 2″ 3.5mm thick coin without any cut outs is approx. 61g.