Just a small remark : the fact that there are parts of a remnant legend on a silver Ecu of Louis XIV doesn't necessary indicate that it's a fake; under the reign of Louis XIV, according to a law, the silver Ecu were struck over older coins of the same size, but with a new type, that was called "réformation".
The old coins were said "récriées", that is to say "not for use in the market"; people have to bear their coins to the royal mint and have to pay a tax for this "réformation". New coins often show traces of the previous legends.
A coin may have been re-struck 2 (or even 3) times...
Successive types are well known and it isn't possible to have a former type overstruck on a later, if you see that, then, sure it's a fake..