Fret Markers
Instruments- discuss specific features, luthiers, instrument problems & questions
I came to the dulcimer without any music background at all. Fret markers were just a decoration and my 1st dulcimer was a kit without markers. I didn't realize they had a purpose until I went to full chromatic fretboards. I looked at the 3-5-7-10 but they didn't make any sense to me [still don' t actually] so went to marking the diatonic frets since that layout was familiar. I suppose, considering they are really just location identifiers, that it's what a person gets used to using [without even thinking about them].
I just looked at my Folkcraft, it's marked at the 3-7-10. Didn't realize that before.

The 6 string fretboard could, possibly, be set up as 2 more, fretless [think chromatic], MD tunings. It looks like the spacing between the middle strings is a bit wider than the others.