The Brevet Martenot Clavi-Harp is an instrument invented by Maurice Martenot, the inventor of the famous Ondes Martenot.
The Clavi-harp a sort of toy piano, but instead of playing it with keys, you play it with your fingers directly on the steel bars. The manner of playing and the sound that is produced is a hybrid of a toy piano and a Hohner Guitaret. The sound is delicate and plucked, with a timbre somewhere between a toy piano and a kalimba.
You can hear what one sounds like at this website: http://www.pascalayerbe.com/martenot-clavi-harp.htm
This instrument is extremely rare and a wonderful addition to any musical instrument collection or musician's toolkit. Don't miss this opportunity!