Here is the link: N#7999
On the Numista web page for this coin, you will see in the References section on the right side of the screen that KM 726 encompasses 520-522.
In the 2023 Le Franc catalog, F.520, F.521 and F.522 are three different coins. All three have Charles X on the obverse, but each has a different edge inscription and/or leaf pattern on the reverse.
Again, I am guessing that the Krause-Mishler system does not recognize these subtleties, and hence classifies all three coins as KM 726. But I'd like to confirm this. Thx.