That is a great sounding dulcimer, Mark!
It's a very interesting dulcimer. It's a double backed Modern Mountain Dulcimer tuned in DAD with an extra low D and an extra low A so it combines a standard DAD with a bass DAD. None of the strings are doubled. However the strings are quite close together, so muting unwanted strings becomes an integral part of the right hand playing technique (sort of like a concert zither).
That's a cool tune but an even more interesting instrument. Can you tell us more about it? Tuned an octave lower? Which strings are doubled?