I hadn't realized that this reproduction appears to have had a long history as a known copy of a much earlier style, so you'd think that there would be no mistaking it, especially by those who are involved with such items.
A similar piece, of exactly the same height, is shown in Daisy Wilmer's book 'Early English Glass' (1910), and her caption to the illustration says........"Opaque-twist Forgery, with Knopped Stem and Plain Foot. Height 6.3/4". Unfortunately, the author doesn't offer any suggestions as to origin.
Speaking of copies and forgeries, Wilmer says of this particular design ..... "shows a better sort of imitation, and one of many which appeared about fifteen years ago; it is illustrated in Mr. Hartshorne's book as an example of a forgery. In this instance the spiral revolves to the right, and has a curious transparent appearance not at all typical of the workmanship of the eighteenth century."
The lady also comments that........"The combined ruby and opaque twist is frequently copied....."
and finally she says of these copies (despite the obvious flaws when compared to the originals).........."purchasers are readily found who are willing to pay four or five shillings (20p or 25p in decimal) for a single glass".
So hope you didn't overpay Chris
I was very surprised to see to see that this type of repro. had been known for well over 100 years.