the other feature of this piece that I thought was unusual - but could just be me being dim - was where the threading continues to the very peak of the lip. Threading, I thought, usually encircles the whole of an object, not something that is only half there as with much of this pouring lip.
Threading is added to a piece, I'd assumed, after the shape has been formed, so adding threading to a piece with a lip of this profile must present other difficulties, especially if produced on a machine.
Would be interesting to hear if someone knows for how long machine threading continued into the C20.
I did think of water jugs for whiskey, but no idea how this was done in the C19 - maybe ceramic jugs were used for that purpose instead of glass.