In Andy McConnell's book, there is a chapter devoted to the 'claret jug', with other examples dotted around in various chapters - and it appears all examples have a lid or stopper of some description (the vast majority have lids), but I can't see one similar to Bernard's with shell ribbing.
Designs range from the rather plain utility arts and crafts designs with silver mounts, of Dresser, through to the traditional ewer shape with narrow neck and on to the French very OTT art nouveau pieces, almost all of which have handles. Zoomorphic claret jugs seem to have been popular.
So, lacking a lid, we might consider that this one is not for claret, and the title might be altered to remove the word.
Incidentally, there are shapes of jugs in S. & F. - described as 'water jugs' - that are identical to the champagne jug shown in Williams-Thomas, and almost the same shape as shown in Mark West - proving that shape alone was no proof of specific use, although it goes without saying that the S. & F. examples are either plain, or without the detailed engraving.
I think the point about the commonplaceness of 'jugs' on the table for champers, claret, lemonade, water or whatever is answered by the caption on page 36 of the Williams-Thomas book i.e. ... 'it was in poor taste to have the bottle on view'. Probably any bottle was considered to be 'common'.
I remember my mother would never have butter, sugar, milk, jam etc. on the table, unless they were in their purpose made containers, and we lived in a council 'ouse.
S. & F. volumes are awash with a very wide variety of claret jug designs - all have stoppers/lids and all have handles.
I'm unable to see the word 'champagne' in the index of McConnell's book, neither does the word 'jug' appear. No need to apologise by the way - we all throw ideas around - until we find an answer, or people get fed up with listening to us rambling