Thanks Joy, I look forward to their opinion
I felt that the cracks on the photo were gaps rather than missing portions on the image so I closed up the gaps with the attached result, makes for a slightly less "robust" person.
Whilst its a complete guess, I don't think the woman in the photo is all that old, perhaps in her 40's or 50's. I have been told the person in the photo was an individual born in 1839 which suggests the image is perhaps between 1880 and 1890 though I suspect a smidge earlier.
She is either wearing a dark bonnet which is close to the top of her head and has decorative side 'puffs' or has a a hair style of similar description. I suspect the latter due to the lighting impyling a centre parting on her hair. This, If Ive read correctly seems to have been popular between the 1870's and 1890's. She seems to be wearing a bodice of sorts (suspected by the vertical stripes which can be just made out) and a chevron patterned shawl.
The shawl is the real hindrance here since it covers up much of the indicators of what fashion (if any) the wearer had on display. The bigger probelm, of course, is that there is no real trend to what the wife of a 19th century coal miner and a god fearing presbyterian Fifer may have adorned herself with, even "for special" back then.
I suspect a better clue to the photo date may come from the photo condition itself, with the fairly rare and faded processing technique . This one has the hallmarks of being a Cabinet Card popular between 1875 and 1895 and (though you cant see it in the copy of a copy I have, there does appear to be an artistic underscore. The sepia tone apparently suggests it is the earler of this type of image i.e. in the 1880's.
It's a shame I cant get hold of the woman who gave me this image (it was a few years ago now) since she could undoubtedly tell me more....
Anyway, opinions still welcome