Wow! I knew these might generate some buzz, but wow.
I don't have the documentation but they absolutely no doubt older than 1900 - like i said they are well-established in the family going least to the great-great grandparents. There's a story about a couple being sat down in those chairs and being told to either get married or quit messing around, so they got married.
The spiral in pieces is because it's broken, the other arm (left hand as you sit in it) is solid (one piece). The reupholstery was likely done pre-1980's since it is quite worn already and I don't think these have seen much use in the last 20 yrs.
Is there any way to distinguish Phyfe original from later copies? Like a stamp, tool marking, anything like that?
I can't get my hands on them right now to feel for spindles. However, in the brief time i was (gingerly) sitting in them I remember a full/solid back - it's definitely not just fabric stretched over spindles.