hi, welcome to the GMB

wouldn't it be great if we could give precise answers to pat question like these - unfortunately, it's true generally that the older the glass the less easy it is to be precise, but will do best to help to some degree.........
a shallow, wide depression where the scar has been removed does indicate circa first quarter of the C19, and barrel decanters for spirits were common enough in that period and a little earlier too, but what struck me as unusual is the notched rim - a far from common feature on these things, although does occur on a small percentage of pieces from around that date. Seen too on some of the very elaborately cut top end decanters intended for royalty and the super rich during the end of the Georgian and Regency time - so you have something a little out of the ordinary.
We're speaking here of notching on flat disc rims as opposed to spirit squares decorated with 'ruff' shaped pouring rims.
If pushed, I'd suggest c. 1820 - 1840, possibly a little earlier, and this would fit with the applied faceted neck ring - assuming it is applied separately - dirt particles down behind part of the ring can confirm this. An indication of a later copy would be a star-cut base, and mould applied neck ring.
As for the stopper........ possibly a mushroom or faceted shape, or even a target/bull's-eye, and in view of the date you won't find a matching number. Missing stoppers, or at least the 'wrong one' are a real problem - possibly seven out of ten found in the wild are affected similarly, and since this is a small bottle you'll probably have a serious problem trying to find a spare stopper that fits even moderately well.
By 'origins' assume you mean a maker ............ but not possible to say unfortunately. I think that in view of the spelling of WHISKY, then the best we can do is to say it was made in Britain............. the Irish and States folk I believe prefer to include the letter e.
these are of course my opinions only, and although we have very few members that collect these things seriously you may well get a better and more accurate reply yet.
