all I can say is that your beer drinking looks to be a little meagre

Am sure that Peter is spot on with his assessment - I think also that a lot of us tend to view small diameter feet as later productions, which I'm assuming applies to rummers as well as wines.
You obviously need Tim Mills' book on rummers - worth every penny (even without an index) - it includes information on this innovative shape, which we're told started life c. 1810, although the majority of examples in the book are ovoids and buckets. I'm not remotely up on rummers, but get the impression that this double ogee shape isn't that common.
Another very useful rule of thumb from the book is that the presence of a
central knop in the stem is almost certainly an indication of C19 manufacture.
I'll take a guesss that your glass is about 5 inches tall.

P.S. for beer, good old Victorian pint glasses - with wheel engraved decoration and some slice cutting, work a treat.