Run few more queries - if you want to be sure get the coin checked because there are fairly good quality fakes available from Chinese distributor: https://www.aliexpress.com/item/United-Kingdom-Coins-1928-CROWN-Britain-Copy-Coin-Copper-Silver-Plated-CEORGIVS-V-DEI-GRA-BRITT/32818779249.html for less than $2 and if they are made from copper then magnet would not help as copper is non-magnetic.