It's a shame the picture quality and contrast are less than good, despite my eternal pleading for plain dark backgrounds when photographing clear glass.
However …….. I think I'm seeing pulley neck rings, which together with the strawberry diamonds and finger bottoms was an overall style c. 1810 to 1830, and mushroom stoppers, as you will know, were commonplace on Prussians from this period. There is some leeway in body shape with Prussians too - the shoulder is sometimes pronounced, but can also appear with a more gently sloping curve.
According to McConnell this was a popular shape across the continent of Europe and the States in the period we're speaking of, though not sure what the differences are when comparing each side of the pond.
Sorry to hear the stopper is doesn't match - are you seeing any matching No. on the body or neck of the bottle?
Were pulley wheel neck rings particularly Anglo-Irish, just Irish, or across the board so to speak? You're also saying that the base is completely flat, without a pontil depression or any kind of radial star? - this seems unusual perhaps - and what in particular suggests a States origin?
Having said all that, always possible that this is a C20 copy - what might there be about this bottle to rule that suggestion out? and what is the extent, if any, of wear? - any seeds in the glass?
I suppose there'll be the usual silence from others.
