Interesting: I was not aware that the St. Etienne proofhouse went back to stamping the city name onto the late-era guns. They did that for a few years in the 1950s and then stamped only the crown/shield proofs. There are just some later Austrian guns that have the full name.
Oh, and the “certificate of authenticity” and the Chamber of Commerce are good ones too. If those clowns don’t know French, the least they can do is run the text through google-translate, which would have revealed it’s a simple proof of proof. Admittedly, these documents do look pretty fancy.