Nickel, 21 mm.
Attracted to magnet: Yes
All of the Y#349 coins were supposed to have been minted in pure nickel at the Shanghai Mint;
However, in 1936 a warlord had the Tientsin Mint produce about one million 10 Cent pieces of heavily alloyed nickel;
The result is that the Shanghai pieces are attracted to a magnet while the Tientsin pieces are not.