1814 Napoleon Bonaparte 20 Francs - Genuine?

Thank you sel_69l for your response.

I have mixed feelings about this coin. It's the last year of Napoleon's reign, so perhaps the mint wasn't as stringent in its coin production? Or as you say, it's possible this coin wasn't made in France.

The Sigma is a wonderful tool but obviously it's not foolproof. It is possible to get erroneous readings on embossed bullion or high relief coins, but this coin does not have those features. I wish I had my calipers with me to test the thickness.

As for an XRF test, I wish I could afford one. I don't have another coin of the era to compare it against. On the same day I did test an 1874 20 Franc Belgian coin and it tested perfect on the Sigma. Both coins are meant to be 90% gold, but the Napoleon coin was way off expected value.

I think someone will snap up the coin at auction on Monday anyway. I have been going to estate auctions for a few years and have never seen anyone test the authenticity of coins. In the past I have spotted some fake Australian 34/35 florins for auction, so I'm always wary of what's on offer.

The coin ended up selling for AU$550+16%, which is below reserve. That is AU$640, or US$429. As the coin contains US$364 of gold that is quite a low sale price.

90% gold coins attract 10% GST in Australia (999 gold does not), so the cheapest possible retail price for a genuine Napoleon coin would be US$400. I have seen generic 19th and 20th century 20 Franc French and Belgian coins sell for more.

I did not bid on the coin as I think it's suspicious. The high Sigma measurement reminded me of a fake Australian florin I have that's made of a lead alloy. I wouldn't be surprised if this 1814 coin is gold plated lead alloy.

Anyway, good luck to the buyer and I hope they didn't get ripped off.