What the Instrument Looks Like:
Typically a hollow trapezoidal prism, with a hole in its center; it has strings strung parallel to the trapezoidal prism's parallel sides.
http://media.liveauctiongroup.net/i/11137/11513176_1m.jpg?v=8CE7CCE485AB530
https://images-na.ssl-images-amazon.com/images/I/417pMfxMN0L.jpg
attached original photograph

Where it Came From:
unknown

Usage and Historical Data:
Very simplified form of harp, usually used as a toy, not in a professional setting.  Usually held on one's lap.  Sheet music for certain types of the instrument can be held on the instrument itself, underneath the strings
http://www.lap-harp.com/melodyharp.htm
http://www.wisegeek.com/what-is-a-melody-harp.htm

How Old is It:
Presumably during 20th century

Who Invented It/When:
Unknown/Unaccredited Inventor
Unknown Invention date

How it relates to items already in the database:

Heavily simplified version of a harp

Written by Isaac Z for GCI