Thanks Elliven. I very much appreciate your help.
Yes, my understanding of the 70 year rules is that copyright expires if there is no family member of the photographer or business to claim ownership of the image. As the image is probably 1900-1910, it's 110-120 years old and I agree that nobody is still likely to complain or claim ownership.
Were you given an original print? If so, I would be able to credit you as the source in my image caption, which I would like to do if you're in agreement.
Once my piece is finished, I will post a link to it on this thread.