If there are the usual striations on the clear part of the bowl then this will have been blown then manipulated - if not and there are indications of mould seams then it will have been press-moulded as you suggest, with all of the cut decoration made when the glass was complete. If you can see the remains of grinding marks on the panels - by using a lens - then they were cut - a type of slice cutting possibly.
The knop looks unusual for a rummer - possibly a cushion knop, and not entirely sure of the shape of the bowl - it might technically be an ovoid which is the most common of bowl shapes for rummers, but it doesn't compare well with others of that shape.
The lower cutting looks to be slice/panel cutting over which is a band of relief diamonds, and all of this surmounted by what look like flutes. Is there a blip on the rim where the scissors would have started and finished the cut?
The heyday of the rummer was c. 1800 - 1850, though they did start a bit earlier and went on for most of the C19 - both unpolished and polished pontil marks seem to go on during most of that time, so a feature not too reliable for dating - if anything those with very flat feet are possibly later than examples with a slightly elevated foot.
I'm not entirely sold on the idea of this being a rummer - it may well be, I'm not expert by any means - but always possible this is a goblet, but whatever, it's a nice glass with some refined features, and as for date I'm going to be very vague and suggest middle third C19 - it's not an easy piece to pigeonhole - then again it might be one of the early C20 pieces - they were well made too. Assume you don't have a copy of Timothy Mills book ?
Let's see what others think.