That can't be the original upholstery, not with the two uneven seams on the lower outside back and the unequal number of nailheads or tacks. I wonder if the back was caned and someone upholstered it rather than getting it recaned? That's a fairly common "solution" to damaged cane.
The back also looks a bit overstuffed in relation to the seat.
Would it be possible to show a photo of the underside of the seat? A closeup of one corner might be enough to tell what's going on there.
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