Ha, ha Clint
It took me quite a while to write my answer since I also checked a number of books while doing so. Never noticed the answers which came in between.
Oddly enough I checked the G-L company since I saw a resemblance to their designs. Looking at the only photo I had (in Le Trait d'Union and part 54 of a series of articles prepared by Charles Claveau) I actually discared the GL-521 as not "good enough".
But since Lucien M. is not only very good at all things Naval he is also way ahead of me when it comes to identifications. (Thanks Lucien!!)
And yes indeed, headache now gone...
Cheers
Stig