there is a flea market today and i saw this

i didn't know what it was at first , and neither did the guy who was selling it
i searched the internet and turns out it's a 'concert zither'.
i already play guitar and i'm thinking of buying that instrument.
he's asking 155 euro's for it. is it a fair price? it seems old and has nothing written on it, no name or date or anything.
what should i do? should i go for it? it seems difficult to play, but i really want it :p
anyone know more about this instrument?