Maybe I should have done it first, but I've now consulted my dating books and looked into the studio and photographer, and it seems that Jim may be nearer the mark than the rest of us, though possibly still a bit early:
Disagree with the date.
I would suggest v.late 1880's-early 1890's.
She's not wearing a bustle which was the dress code in the 80's.
She also appears to have hip-padding which first appeared late 1880's.
His dress style was typical throughout the 1880's & 90's.
Costume isn't really my strongest point, but one thing I picked up from Jayne Shrimpton is the more elaborate bodice from about 1888 onwards, sometimes with a plastron. From about 1890-92 there's also a subtle puff at the top of the sleeve, which in the following years became a full "leg of mutton". This became smaller again from the mid-1890s.
The photo I posted was from an old scan, and I've now found the original, which gives further important clues for dating. The reverse of the mount lists Allen Nield's studios as:
Queen's Arcade, Leeds
Lindenthorpe Villa, Linden Road, Leeds
65 (late at 105) Market Street, Manchester
68 Wellington Road South, Stockport
111 Brook Street, Macclesfield
I've found references to these as follows:
Queen's Arcade - 1891 census and electoral rolls from following years
Lindenthorpe - 1896 electoral roll (residence?)
Manchester - advert for assistants in Manchester Evening News of 7 July 1894 with address of 105 Market Street (nothing found for 65)
Stockport - Stockport County Express of 6 Sep 1894 mentions recent opening of studio there
Macclesfield - nothing found
So it seems that the mount must be from about 1895 or later, and I don't think the couple's clothes or appearance would totally rule that out. Samuel was born in Nov 1854 and his wife in May 1857; I could see them as having a few more years on the clock than in 1883, and by then he was definitely an insurance agent rather than a miner.
I've also considered whether it might be a reprint of an earlier photo. In the 1881 census Allen Nield was a coffee tavern keeper in Hadfield, near Glossop, and he was still there in July 1887 (newspaper report of his son drinking poison (fatally)). The next reference I have to him elsewhere is the 1891 census as a photographer in Leeds, plus an 1891 electoral roll at a different address in Leeds which didn't give an occupation. So if he took it himself, it can't have been earlier than about 1888. He could in theory have taken over an existing business in Leeds with all its old negatives etc, but that would need further research.
And the pose? According to Robert Pols' "Understanding Old Photographs" it was popularised by Queen Victoria, but there were aesthetic considerations too. As I'd wondered, the relative heights of husband and wife could be a factor, but having the wife standing allowed her dress to be shown off better. Her figure was also rather more likely to appear as a graceful and flowing part of the composition than that of a man in what may have been a rather shapeless and baggy suit.
Anyway, thanks for all the input so far. Any further thoughts are of course welcome, but for now I'm not sure whether I can say anything more precise than 1888-96, with earlier dates being a reprint with an 1895-ish mount - so not their wedding photo, but possibly to mark some other occasion as yet undetermined.
