Glassmarken Lexikon can be wrong but I don't think so this time - they have exactly your signature as Quenoil! -and yes they say it reads like Quenvil (at which point my German fails)
We're probably talking about the same signature but neither Lexicon nor interestingly 'Legras Verrier' think its anything to do with Legras -there were loads of enamelling establisments at the time copying Legras, etc etc
I guess it would be sad if all books agreed.
cheers
Mike