Hi Jim, Prue, Igor, etc
It is definitely my Isaac as the original was held by my Fathers cousin, passed down from his Mother. I can see that he looks like one of those old Russian photos, but I'm pretty sure he was born in Ayrshire, Scotland. His Father Robert Crothers was born in South Carolina to British Parents. It has been suggested by family that Isaac was a Quaker but I have never found any proof.
As I said, the original photo was owned by my Fathers cousin but he died over a year ago and I assume his son has the photo. He hasn't responded to Christmas cards or other communications so it may take a while to contact him. I will post details of the reverse as soon as I can (if I can!).
To me, the thing round his neck looks something like woven string!
thanks for all your suggestions.
regards
Peter