items such as tumblers and decanters, from the period which Ann's links now suggest this originates (late Georgian and Regency) tend to have wide but shallow depressions where the pontil scar has been removed.
Looking at the base of this piece it appears the depression is wide and shallow, but not entirely sure as the pix lack contrast and not easy to see, but am sure you will tell us if this is the case.
Photographing clear glass is quite an art.
Of course this glass may have been in granny's cabinet for eons, since it's a novelty item and possibly treasured and not used, but generally there would be appropriate 200 plus years of wear on the narrow band of glass on which the piece sits - the footrim.
If you angle the base to see this in reflected light, the depression should show the remnants of the grinding marks, however faint - they never seem to be removed completely. You should be able to detect these lines which will all run in the same direction over the entire width of the depression