hello roy.
just personal opinions, but I wouldn't have thought for sherry - more likely claret or wine - and I'm going to disagree with your dating based on the handle which appears to be a bottom up attachment, rather than a top down variety - tell me if I'm wrong about that. The former was the norm after about 1860 ish, so I'd suggest the date of this is much later than you're thinking.
From what you're saying this may well have been a blown-moulded piece, which creates the optically moulded effect, then transferred to a pontil rod to finish the rim/pouring lip, then finally the handle.
These things can pick up a lot of wear quicker, perhaps, than other items - leading to the thought that it has greater age than it actually has.
I doubt that you'd find a maker. The colour might suggest a Continental origin, but it could be from anywhere - I take it there isn't a matching No. around the neck area? Bohemia perhaps.
sorry not much help, but decanters can often be impossible to pin down.
