Originals are exceptionally rare, but it is a very popular reproduction coin because of it's rarity & unusual design. I can find a few listings on ebay starting at around £5. Even ones with silver plating.
Originals are 92.5% silver. Any jeweller or dealer will have tools to check metal content.
You can also check weights & dimensions yourself. If it's made of other materials, they'll have to have something wrong. Reproductions usually get the diameter right, but either the weight or thickness wrong.
I would almost certainly say yours is a reproduction. It looks too bright (silver tarnishes over time), and as discussed, originals are really rare.
Beyond that, something just looks wrong. I can't put my finger on it, but probably something in the detailing.