Counterfeit Detection: 1915 Austria Ducat - Restrike - .999 Gold / 24k - Jeweler's Copy

First forum post - just joined as I thought this needs to be posted somewhere!

A week ago, I picked up seven 1915 Austrian Ducat restrikes from an LCS that's been in business over 50 years. Each was in its own flip coin holder and they all looked fine - I even confirmed that they test every coin. At home removed them from the flip holders, as I just keep them stacked together. I noticed that one was a hair wider and a bit thinner, but immediately figured that it could be a variation over the 100 years of these being minted - or even an actual 1915 non-restrike.

Upon weighing each, the other six weighed exactly 3.49 grams, as they should. The odd one weighed 3.54 grams. Many Austrian ducats have been weighed on my scale over the years and none less than 3.48 grams and none more than 3.50 grams. Something was up. It only measured .76 mm at the thickest section whereas the others all measure about .80 at their thickest sections.

It did look really good until I examined it very closely. I eventually noticed a few small, but significant differences. Eventually, I found many tiny differences.

The most significant, see pics, was a missing dot on the back between the "ILL" and "REX" text. I looked online and no year Austrian ducat was missing this dot. I then noticed that the dot after "GAL" was too low. All other ducats had the dot in the middle of the "L". Eventually, I noticed other differences like missing smaller dots, a missing tongue on one eagle head, hair and ear differences on the front of the head! I figured it was a fake made of either pure gold or tungsten coated with gold.

I took the coin back to my LCS. They chalked it up to different dies over time and XRF'd it again. They casually mentioned that it came back as .999, 24K pure gold. I reminded them that it should test as .986, not pure. They took it back and retested along with another ducat and confirmed that the suspect one was .999 and the other was .986. They didn't concede it was counterfeit but did honor my request to swap it for another (genuine) ducat.

In hindsight, I probably should have kept the .999 fake. Perhaps it has some historical value? Has anyone else seen anything like this? I couldn't find any info on this happening with a similar ducat.