I'm sorry I can't comment on it being Legras as I don't have the books unfortunately. All I would say is that the shape and decor of the Gilded Curio one appear to be a very good match to yours and they have confirmed it is identified in the Legras book as Legras .
I think this is an area where if I were to buy one of these vases in this decor I would want it to be signed Leveille to be honest. My reasons are that there are two in Cappa as I mentioned, both identified under Sevres, however both are unsigned. The second one, the ewer, the decor looks very similar to the body decor of the Leveille vase for example, but it also looks very similar to the one now id'd by Gilded Curio as Legras.
I think the only other thing I would do is to try and pull out pics of signed Leveille pieces (and it's acknowledged that his vases were not always signed) and try and look at the gilding and the decor on the body of the vases and the shapes and see if there are any matches or real similarities. Legras did not always sign their vases either - I have three unsigned.
It will be difficult if Sevres, Legras and Leveille made vases with a similar decor but it's just possible you may stumble across something, however at the moment it's looking most likely that your vase is Legras unsigned, from the information given by Gilded Curio.
Whichever way, it's a beautiful vase

m