The one that has been identified in the black and white photograph of Ricke in the link I gave. It's the one on the left. The same design as your jug. Ricke id's it as Loetz production number 3175 according to the owner of the site if I have read it correctly. The owner states there were other makers who made similar designs but that design number 3175 was id'd in Ricke, I believe as a Koloman Moser design?
So if you photograph yours in the same angle as that one is it would allow some comparison. Otherwise it's very hard to see the shape outline - and it appears there were others made in that design that might be more similar in shape to yours perhaps?
So far, yours has a pontil mark, nicely polished, has a firepolished rim if I see it correctly, and has an integral hollow handle as part of the jug. The shape looks very similar to the Ricke one, but yours does look from your photograph, as though it tapers significantly narrowly at the bottom. A photograph at the same angle might help dispel this thought.
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