Jeff Sims Antiques has dated this piece to the 18th Century.
The foot is of rounded form and the pontil is rough snapped as you would expect at this period.

Monteith and bonnet glasses were most frequently used for serving desserts at the dinner table, often of liquid type such as syllabub. They were amongst the most frequently advertised glasses during the mid 18th century, although their numbers appear reasonably scarce today. Dimensions below.
Postage and packing £10.00 UK
£18.00 Worldwide
Condition :- Excellent, with no chips or cracks.
Origin :- Anglo/Irish
Date :- c1770.
Height :- 7.5 cms.
Diameter :- 6 cms.
Jeff Sims Antiques has dated this piece to the 18th Century.
Specialists in antique silver, glassware and objects of vertu
You can view the stock and full dealer information on the Jeff Sims Antiques Profile Page