Nice find for the origins of the painting. I don’t disagree with anything regarding the painting and a possible age of late 19thC...except for a small fly in the ointment which is the mix of styles. In the engraving on the jug taken from the painting, the dancers around the changeling/puck are the fairies yet on the glasses they have also shown a more modern depiction of fairies with wings. That is a mix of two different styles, not a pure copy of the painting.
According to the fairest.com, wings were first illustrated on fairies in around 1800 but they also say “Twentieth-century fairy sightings often describe beings with wings, something that would never have happened in the nineteenth century”. I don’t imagine the engraver would have mixed styles by adding the winged fairies unless they were familiar in popular culture at the time? It’s as though the winged fairies were added so that the subject was understood. Maybe early 20thC?
I think there are fairies with wings on the jug as well. There appears to be two in the most recent pictures? And possibly they aren't fairies but cherubs instead?
Artistic license to represent as the artist wants to. They may or may not have bowed to popular culture. They may have been depicting fairies with wings as per around 1800, or their understanding of depictions they'd seen. Perhaps it was early 20th century and got mixed up with tinker bell? Always possible. I don't know what the source of that information from Fairest.com is about fairies never being described as 'with wings' in literature of the 19th century.
If we read the information Sotheby's have put on about Dadd and the acceptance of his paintings, it shows a great breadth of artistic license and mixing of inspirations as subjects and within the paintings.
Also this description indicates this painting was about Puck and so too the nature of the subject for the jug and glass, rather than it being about a 'changeling' (I don't like to think of these items as being about a 'changeling'):
'
The pictorial treatment in both of Dadd's Dream paintings was, however, entirely personal and thoughtful. The symbolical imagery represents a meditation on the play itself, which makes constant reference to moonlight and moon imagery. Dadd too uses the moon to magical effect, placing it as the source of light behind the figure of Puck and leaving the foreground mysteriously shrouded in shadow, with a back-lit border of foliage and sparkling dewdrops framing the front of the composition like a proscenium arch. Beyond the darkness Puck, encircled by dancing fairies on a grassy stage, is picked out by the cool moonlight, emphasising the theatrical nature of the scene: but it is also a view into a miniature landscape inhabited by elementals who are more akin to classical nymphs and dryads than the elves and pixies of many of the artists who followed in this genre. If the childlike figure of Puck at the centre seems slightly incongruous in this company, a sheet of pencil sketches (Fig 2. sold in these rooms, 24 November 1977, lot 74) shows that he was originally intended to hold a bow in his left hand, suggesting that Dadd wished him to be seen also as Cupid, the true presiding genius of the play. 'Interestingly, I still maintain the face in the painting of 'Puck' by Dadd, looks like the face in the depiction by Sir Joshua Reynolds and definitely reminded me of the face of the adult Puck in the painting of Puck by William Blake.
https://www.tate.org.uk/art/artworks/blake-oberon-titania-and-puck-with-fairies-dancing-n02686 Perhaps the Blake and Dadd depictions came from inspiration from the Joshua Reynolds engraving?
I can now see the engraving all the way up the outside of the handle of the jug. I'd say that was Bohemian in style.
I think having larger and clearer photographs is necessary for any further understanding of the engraving etc. to be honest.
That jug handle shape makes me think Bohemian production for some reason,as does the style of engraving. I'm thinking Harrach specifically, but other possibles might be Lobmeyr or say Riedel?? However there were many Bohemian engravers here in the late 19th century for example, so it could be piece made in England or Scotland for example, but engraved by a Bohemian engraver perhaps.