Hi there! Theres a coin, which colour makes me believe its made from copper. Its weight is 2.9 g and the diameter from 26.7 to 27.1 mm. As far as I understand, metrics fit the genuine silver coins of Wenceslaus IV but Ive never seen a silver coin like this. Any ideas on how to clarify this?

Obrázky:

counterfeit from copper?
may be - but i am not sure
the lion and the reverse dividing mark look exactly like on the original groschen type of Hána VII.
it doent indicate a forgery

how to clarify this? by material tests