That's very exciting. Dags lasted longer in the USA than elseware but they would have been 50 year old photo's when she was born. How many of us are so fortunate to have such a family tradition.
Dags can be photographed but it is difficult because they have to be seen on an angle to be viewed, as you know, and reflections have to be avoided. Polaroid filters may help with the reflections. It just occurred to me that tilt shift on a large format camera might help with having to view on an angle. I would avoid taking them apart to photograph if you can.