hello David - whilst we wait for Peter to look in, hopefully, I'll do the head on the block bit.
The obvious features of your glass are not in themselves wrong for the C18, but I'm wondering what it is that makes you doubt that this is a correct period piece - you don't say.
The part honeycomb moulding (whether diamond patterned or more hexagonal) is o.k.......... the air twist spirals in the more common direction so not a problem.......the foot looks (but difficult to see exactly) to be domed.........apparently the snapped pontil started to be ground smooth from c.1760 ish.......round funnel bowls like yours have arguably been the most common bowl shape............the overall height is about right.
So how about the possible down side.........if it's an English piece it should be lead glass, and when pinged should ring well. The bowl shape, although r.f. (round funnel), looks exagerated at its base - looks more like a C19 sherry or port bowl, possibly. The colour of the glass, in pic. three, looks very white, perhaps lacking the oily grey colour you might expect from c.1770 ish, and although knops come in a myriad of placements on the stem, this pair look a tad unrefined. Try flicking it first - if no lead ring, then you may have a problem.
No chance of finding out where it was made, unfortunately, and unlikely you'll ever see another one. You say nothing of possibly wear, or whether you are suggesting a C19 or C20 copy. Copies of forgeries are made only when there is a market for them, or when the originals have reached a viable market value, to warrant copies being worthwhile. Regret I know nothing of copies of these things..........they may have been coming from the continent in recent decades but I really don't know.
So, what was it that made you suspicious, and where did you get it from