hello Fred - I think these things often confuse us - am sure you've seen our past dialogues attempting to date such pieces.
Drams, I think, mostly had smallish bowls, although conical does occur occasionally with them, but my gut feeling is these might turn out to be small wines - just a feeling.
What appears less than common is to have those 'slanting blazes' (your feather decoration), sometimes known as a herringbone fringe - toward the top of the bowl on a glass such as yours. Blazes were a common Georgian feature around the base area of tumblers and decanters during much of the Georgian period.
If pushed I'd go for 1830 - 1850, but that's really only a guess - sometimes it's a gut feeling and looking at the overall appearance of the glass.
Your knops, collars, bowl shape, snapped pontil, pontil depression, slice cutting - are all found on drinking glasses from 1770 to late in the Victorian period - so life isn't easy
sorry to be of no real use.