This is a very good English hand blown, Georgian drinking glass, sometimes called a "Dwarf Ale" glass, which we date to the mid-18th century. 
This glass is individually hand blown, from lead glass which is characterised by its soft grey colour, its fairly heavy weight and the imperfections that occur naturally within the glass as part of the hand-blowing process.
The glass has a very good conical round funnel bowl which has been wrythen (twist fluted) along its length. The bowl sits on two (double) wrythen cushion knops with a short stem below, supported by a basal knop. The foot is plain with a good thickness and large diameter with a snapped-off pontil to the underside.
Dimensions in inches:
Bowl diameter 2.5, foot diameter 3.13, Height 5.5.