TC, this is old, I am not certain just how old, but it would be at least 150 years or maybe 250 years. It is a wine glass, trumpet bowl, plain stem on a conical foot.
In my first flush of collecting I started with 18th c drinking glasses until the price of those drove me to more recent and cheaper glassware. One of my early purchases was a copy of L. M Bickerton's book (read bible) "Eighteenth Century English Drinking Glasses an Illustrated Guide"This covers virtually every known shape and style of drinking glasses made in the 18thC. To quote Bickerton on the subject of plain stems,
'Though plain-stemmed glasses, many of them of simple, heavy manufacturer for tavern use, persist throughout the middle fifty years of the century and form the least avidly collected group, they display surprising variety. The majority have trumpet bowls, the stem often enlivened by a long tear and occasionally by the addition of collars. No problems of description are encoiuntered save that of distinguishing between two- and three-piece glasses. In the two-piece form the bowl and stem are clearly made form the same gathering of metal, no weld or joint between bowl and stem being either visible or possible'.
However, on your glass the foot does not appear to fully meet the usual 18thC design of being equal to or greater than the diameter of the bowl rim. But as there seems to be some damage to the rim, it is possible that the foot was also damaged and has been ground down. If that is so then the glass is most likely to be 18thC. However, the Victorians also made good reproductions of some 18thC styles the plain stem being one of those. In such a case then the foot would follow the 19thC pattern of being smaller than the Bowl rim, which if that is the case of yours, then lose around a 100 years in its age.
Whatever, it is old, and as Ivo states it is far too big to be a firing glass and the foot too fragile as well.
Bickerton's book was published by the Antique Collectors' Club and should still be available if anyone wishes to buy one
GeoffT