you may be correct yet with your first suggestion, but you learn to be cautious when attributing dates.

Unfortunately, the silence from the response is deafening - which is not unusual here, and shows that most other folk are either not interested in this period, or just being cautious, especially with run of the mill C19 drinking glasses. Having seen acres of these things, I've a feeling that the short answer is that there isn't an easy method of accurate dating for most Victorian pieces in general.
Most books tend not to treat this period seriously, so they terminate roughly with the demise of George IV - c. 1830 (the end of the Regency), but there was one book I've now parted with that was of some use in this area, and oddly it was inexpensive. John Brooks produced something called 'The Arthur Negus Guide to British Glass', and although it was a general overview only, did cover pieces similar to yours, and with some pix, but as usual it can't be accused of giving a great deal of space to such things. I think there was another by Tony Curtis 'Glass and Metalware' which gave some pages to Victorian drinking glasses, and again it wasn't expensive. These books are available on Abe Books.
In the end it's a matter of assessing every feature of the glass - colour, seeds, foot (possibly the most important part of a glass), bowl, stem, ping, cutting/engraving etc., and handling them at fairs/markets - without dropping them

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The term early glass should be reserved for C18, in my opinion.