My own Rudall & Rose #4683, London made c1843, cocus with sterling silver: stamps on Bb and G# touches under springs, appear to be a "J" elided (sharing the same main stem) with an "R" (perhaps for "John Rose"?), though I note from Terry's web-page these are most likely partial examples of the "RR" ones shown there, with only the serif of the foot of the first R showing.
Wylde, "from Rudall & Rose", London c1840s, cocus with silver: stamped with an "F" on Bb and short F touches and x2 on low C# on touch and shank, which also has some job-marks (as does the low C, not shown). The long F is missing.
Eastes/J Fentum, stamped "Cambridge" but probably retailed there by Eastes, made in London by Fentum, c 1850s, cocus with silver: stamped "F" on Eb touch; stamped "H&I" on long F (very weak), low C# and Bb touches, maybe also on G# touch, though that is unclear - could be a botched "H&I" or just possibly "AL", though I think that unlikely - the apparent "A" is rally a composite of other tool marks/casting inconsistencies and perhaps part of the "H".
Metzler, London, probably 1850s-60s, cocus with German Silver: stamped "AL" on long C and Bb touches.
Anonymous English 8-key (my ref #51), unprovenanced, mid C19th, cocus with German Silver: stamped "F" on low C# touch.
Anonymous English 4-key (my ref #56), unprovenanced, mid C19th, cocus with German Silver: stamped "I dot I" or possibly "[ dot ]" or even a vague square with central dot to all three extant keys (short F missing) - Bb, G# and Eb. These could well be weak examples of the "I dot N" or "I dot F" Terry illustrates. (Edit: actually, now I know I'm looking for it, I think I can just about make out the Ns in at least two of these, and more so in the photos than in reality. Ditto the first Rs on my R&R)
Manipulated close-ups of the Bb key trying to clarify the stamp:
Anonymous English 8-key (my ref #59), unprovenanced (Metzler/Liddle style), mid C19th, cocus with German Silver: stamped "AL" on low C#, Eb, Bb and both long and short F keys.
That's it for now. I have three other mid C19th English flutes here:- another anonymous Metzler style 8-key with Liddle style keys, but totally unstamped; another anonymous 8-key in a different style, also stampless; a Wolf & Figg (London) which has body stamps but no key markings. All are cocus with German Silver.