Horse car.
There are not so many informations about this tram: it was made towards 1890 by the factory that will become the "OM" for the "Belga" (Atm never owned horse-trams) and was used till the Second World War years as service trailer.
Historical, reconstructed in 1978. Visible at Sassi station museum. http://www.atts.to.it/it/veicoli/tram-statici/197