Problem with coin weight 50 marek 1923 KL. (Poland, II Rzeczpospolita)

I have a problem with coin weight 50 marek 1923 KL. (Poland, II Rzeczpospolita). As shown below, I am in the possession of such coin with weight 4.3g. And this does not match to any known material version of this coin. What this coin might be then?

It would fit with the bronze version but the weight

N#126796

Frenchlover

It would fit with the bronze version but the weight

N#126796

 

Yeah exactly, the weight is strange. Maybe composition trial?

Or just a copy.