You have a beautiful example there Richard - one of the best I've seen, superbly struck up compared with the average example.
HOWEVER... even at a glance I can see the differences on the reverse. From the eyebrow height of the helmet and head, down the neck, to below the breast area, and the drapery adjacent to the shield - it's all more vague and less precise, which is inevitable when you consider the deep cut portrait on the obverse. Which is why I sigh admiringly at your example, which is so obviously genuine, but would run a mile from the other which is just too precisely modelled to be anything but fake.