Brass standard meter, engraved with the signature of the maker, Ferat. The length of this standard is provided either by the ends of the bar (which has two recesses for the purpose) or by the distance between two lines engraved on its surface. The date of manufacture was determined from two letters from Francesco Favi in Paris to the Superintendent of the Museo di Fisica e Storia Naturale of Florence, Giovanni Fabbroni, who had commissioned the purchase of such an instrument.