Well, I am not an expert on that particular coin, but it neither looks right nor does the story make sense. Just my opinion.
Why do you think that it's not looking right? What story? He bought it from an an aiction house based in
Paris, years ago (invoice here) and sold other coins to me and a coin seller I know. These were surely original. So if its a fake, I'm pretty sure he doesn't know. It's not
plated amd like DinX (big thanks for that!) wrote, it's silver under the chip which is oxidized. So now that I know that it's oxidized/crystallized silver I'm nearly sure it's right.
Crystallized silber should be hard to fake, so it's not new. If it is an ancient fake, why is it silver and not a copper core? A fourré is rarely in this
good condition (especially the surface). But I'm not Sherlock
Holmes,
nor Jesus - I might be wrong with my theory. But I don't see a lot of other possibilities.
Greetings,
Joel