As the article suggests, the Mt Louis Solar oven was a prototype that lead to the real godzilla, the Odeillo Solar Furnace:

https://en.wikipedia.org/wiki/Odeillo_solar_furnace

This thing is massive and a beauty to look at. I remember going through the tour in the 90s, there were very thick steel plates on display that where melted like butter in the center it was really impressive. https://books.google.fr/books?id=VQEAAAAAMBAJ&pg=PA88&lpg=PA...