***
Hi m.
One problem with attributions is that different people have different views - so a shop such as Libertys and an auction house like Boisgirard may not agree with each other, or with some collectors! You only have to look at eBay to see just how off the wall some attributions are, and the big auction houses can be badly wrong too. I have seen some strange attributions by Bosigirard and by Bonhams, for example.
As alpha indicated, Philippe Frère wrote the best article on Grenelle, in last year's PCA Bulletin. That included 63 images, mainly of Grenelle pieces. There are no identical cane matches to yours, but the white shard rose is quite similar. Paul Dunlop gave a talk at Wheaton in 2012 where he looked at a whole range of antique European weights, forming 14 different groups, most of which are not yet attributed to factories. The canes in yours match some in weights he referred to as 'Factory 8'. These pieces are not from any of the big 3 factories, and probably not St Mandé.
I think the best guess on yours at the moment is French, factory as yet unidentiifed, possibly Grenelle, possibly not!
Alan