his is a good, tall hand-blown, English, mid-Georgian, cordial drinking glass with a single series opaque twist (SSOT) or Cotton twist stem, dating from the middle of the 18th century, circa 1765.
These glasses are very collectable. 
It is made from English lead glass which is relatively heavy and has a soft grey color, with age related wear to the foot rim as expected with over 200 years of use. The glass has the usual striations, inclusions and tiny bubbles you would expect to see in 18th century glass, which gives these glasses their unique charm.
 
The glass has a small round funnel (RF) bowl and is typical of a cordial glass, having a proportionately smaller bowl than wine glasses of the same type. The bowl sits on an excellent tall, single series opaque or cotton twist (SSOT) stem with a lovely medial swollen knop. The stem leads to a good wide conical foot having a rough snapped off pontil mark to the underside.
Cordial glasses are rarer than wine glasses and single series twist stems are earlier and also rarer than the double series twist, both these factors making this glass a more sought after drinking glass.
 Dimensions:
 Bowl rim diameter: 1.82 inches.
 Foot diameter: 2.69 inches.
 Height: 6.25 inches. 
This glass has a slight manufacturing fault to the base of the bowl on one side, where the bowl joins the stem, over a 7mm section, please see final image. However the fault does not go through to the inside of the bowl and the glass has a good ring to it when tapped with a finger Structurally sound. No restoration. 
 
Diameter
2.69 in
Height
6.25 in