Big extrapolation to get to an "Orkney guitar style" from a photo of 1 musician, I would have thought. Can't help with this one, I'm afraid Dick - not something I've ever been aware of. Best Orkney guitarist I've come across is Jennifer Wrigley, [ or is it Hazel ? - that long since I've seen them ] - but she is very Shetland influenced.
By the way - someone was asking about advice about concertinas in a thread earlier today. I suggested you might be the man to help.