It is indeed strange... Three characters are missing. Most likely, they weren't printed on the paper. In that case, if you still have the receipt, you can confidently return the disc to the store.
By the way, are you having this issue with all the keys? Or just for Tribes of the East?
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Here's the thing, could you help me out? I lost the key for Heroes of Might and Magic V - Tribes of the East. Could you provide it if it's not too much trouble?