thanks for sharing Anne - attractive pieces - thanks also for attaching the link where Gammon's design had been discussed previously - before my time on the GMB I think, and Bernard's input very interesting.
I have a 3.25" version of this tumbler, unmarked, and in uranium as shown in the attached pix, although regret I'm puzzled by Charles Hajdamach's comments in his book 'British Glass 1800 - 1914', where he says (page 335 - plate 302) that......."Plate 302. Left and centre. Tumbler and matching pickle jar, press moulded by Thomas Gammon, Birmingham, 1849". Looking at the tumbler and pickle referred to by this author - plus my own examples of both - it's my opinion that these two designs do not match remotely, so I'm confused as to the origin of CH's attribution of Thomas Gammon for this design.
In an effort to resolve this I've looked at what I believe are all of Gammon's Registrations (around this period) in Slack and cross checked with my pix from Kew, and although I appear to have copies all of Gammon's designs for three years starting with 59584 (18.04.1849) through to 82737 (10.01.1852), I can't see a Board of Trade application/Registration for the design of the tumbler shown in Hajdamach (and owned by Anne and myself).
The answer may well be quite simple, and it could well be that the tumbler was a separate design that was never Registered - perhaps someone is able to help me with this matter.

My copy of this mystery tumbler is unmarked, the base of which is distinctive, and should make identification very easy.
Looking at those early Registrations from Thomas Gammon, there appears to be only one design which was submitted in the shape of a tumbler, and that is Rd. 62918 of 12th October 1849 (the horizontal diamonds) - i.e. the one which pipped Richardson to the post, and about which Bernard has already written so interestingly.
Also hope you don't mind me sharing a pic of my variation on Gammon's rummer - the same design as tumbler Rd. 62918 (the horizontal diamond pattern again), although mine is not quite as shapely as yours. On my example there are three mould seams and it has a ground/polished pontil depression - it stands 5.3/8" (c. 135 mm) tall, and is again unmarked.
On his original drawing, for the tumbler (Rd. 62918) - which Gammon submitted to the Board of Trade, he wrote....."ornamental design for tumbler and articles in glass, which does appear to confirm the comments that this design was applied to more than one article, and I can add a copy of the Kew image (for 62918) showing the original drawing, if anyone considers this is worth adding the the thread.
I'm sure I have the jelly somewhere, so will post a pic if I can find it, but I've yet to find the pickle.
As always with such items, the actual date of pressing remains speculative - I've no idea for how long Thomas Gammon used their moulds.