Don't know Pete that you're going to get very far with this one, unfortunately.
Have you looked very carefully around the lip area, the neck (inside as well), and even on the base, for a 'matching No.'? - and assume there isn't an acid backstamp somewhere on the base.
You may well be right about the carafe idea, and I'd suggest this is a mallet shape - not perhaps one of the most common shapes for a carafe.
Early carafes, apparently had wider mouths than decanters, but yours I'm sure isn't that old - circular and oval punties were around for a long time, and the 16 point star - although a feature of decanter bases around 1830 - 40 has, like most decoration, been copied since.
You don't comment on wear, which should be quite noticable on something of the age you are suggesting. Might have originated almost anywhere.

P.S. Trees don't make the best backgrounds for pix by the way.
