Yes, that one is interesting. I've never been able to find any more information on that picture/plate in the book which shows the dolphin tazza, as to where that tazza was shown/pattern number reference or anything. I couldn't see any more information in the book on it either. It is however a large and detailed book so I may have missed it. But from the caption under the plate it does not seem to specifically state it's Richardson's although it comes under the chapter' The Richardson Dynasty' in the book.
My hesitation is also because, in that Colour Plate 10 in the book, there is shown a dark red streaky salt cellar. It's facet cut and to me looks very much as though it's Bohemian red hyalith glass.
The description says '
The salt cellar matches the design illustrated in Plate 61 while the....' Except that whichever way I position it, whilst looking at the photo of the piece in the book and comparing it to the design drawing in plate 61 I cannot see it matches the design in Plate 61. So I have been wondering whether it's actually Bohemian red hyalith.
And yes, I can see the dolphins in that tazza look similar to the OP's dolphins. My questioning in my head has been over the intervening years, is the red tazza with the dolphins which appears under the Richardson Dynasty section in the book, actually a Bohemian piece?
Awkward

. I don't have the experience or breadth of knowledge, or authority to question really. However there's something about both those pieces that doesn't sit right at the moment. Probably it's just lack of evidence and I'm wrongly questioning them. But maybe they are Bohemian?
And you can see why I was questioning in that thread link you gave:
Because the dolphins on the bowl in the book and linked to the Dudley museums collection tazza,look similar to the dolphins in the link I gave to the piece sold as Mount Washington/Moser here
http://ancientpoint.com/inf/35790-rare_19thc_victorian_cranberry_glass__figural_dolphin_vase_mt___washington_moser.htmlAnd I'm pretty sure that piece is Bohemian.
There are only a few pieces identified as Richardson in the online Black Country glass collection. Looking through all the pieces there are even fewer which include ruby glass to provide some form of comparison. None of the ruby glass items are comparable to the tazzas. In terms of the panelled gilding there is one other piece in the collection that has this vaguely similar type of decoration - a very bright green jade glass jug here:
http://blackcountryhistory.org/collections/getrecord/DMUSE_ST140/