Hi Richard; I dunno how I missed this when you first posted it.
Yes, AFAIK, there were quite a few of those narrow trapezoid shaped dulcimores built 'back in the day'. I have a suspicion that they were part of that transition from the scheitholt/PA zither to the dulcimore -- basically an 'old style' body with a new fangled central fretboard. As always, there seems to have been little standardization, except perhaps by region. Some had a simple pin block type head for steel pin tuners, others had elaborate scroll heads with violin style tuners, some had scroll-headed pinblocks! Some were shallow bodied, others nearly square in cross-section.