Sedayne -

I don't know that the history of the mountain/Appalachian/lap dulcimer is well enough known to make any general statements about how the earliest ones were strung.

A fair number of old ones are known with very primitive peg tuners, and the style and (lack of) fit would be better suited to a gut string or at least to very slack-tuned metal string. Many (as a percentage) of the old ones were quite obviously one-off homemade instruments, and could have used any string material(s) handy.

Some tradition asserts that they were played almost exclusively as "solo" instruments and some say that the main use was as "courtin' instruments." For the latter application, loud wasn't needed - and probably not wanted - since the instrument only needed to make enough noise so that the chaperones could tell the couple was still playing and not playing around, while still giving them some degree of privacy for the smiles and winks and drooly stuff that was "permissible." Gut strings, or even binder twine or old boot laces, would have been quite sufficient if that actually ever was a common intended use. (Of course that assumes that little brother didn't have his iPod blaring away in the kitchen.)

There are sufficient surviving "pretty old" instruments to offer some clues as to construction in a few fairly specific times/places, but the ones that survived probably were only the best, and nobody knows if they represent a majority type or are really similar to a significant percentage of earlier ones.

Was Stradivari actually a perfect builder, or did all his "less than good" ones just get neglected, busted, or chucked in the lake? The ones that survive are all good (with one(?) exception, I'm told) - after the modern modifications, of course - but they're not even close to a majority or even a representative sample of the ones he built. We don't really know what his "average" instrument was like.

John