Puts me in mind of a string-drum; if you tuned each of the strings sets to a different chord it would be nice with a three-hole pipe. I've draw up plans for such things in the past but never gotten round to construction.

Might not be a musical instrument as such; in antiques shops I've come across beautifully constructed metalophones tuned to a chord which were used in lieu of dinner gongs, and one crude zither of four or five strings which once served the same purpose in a guest house.

Curious piece though, not least for the trough-like construction - and one wonders if those two large marks on the sound board are indicative of an earlier string arrangement?