The mathematics professor Tito Filippo I. B. Gonnella (1794-1867) in Florence almost certainly built this very solid, exquisitely executed dial adding machine. Another adding machine with setting keys built by Gonnella is in the Museo di Storia della Scienza in Florence. Both of them are described in his book published in 1859. In 1816 Gonnella, who obtained a science doctorate in Pisa, published a treatise on the manufacture of parts for mathematical instruments. In 1818 he was a member of a Florentine commission to undertake a new land registry of Tuscany by order of the grand duke Leopold II. From 1829 to 1850 Gonnella taught mathematics and mechanics at the Accademia di Belle Arti in Florence and subsequently mathematics till 1854. In 1851 he exhibited his planimeter at the World Exhibition in London and was awarded a first class medallion. In 1861 he received another medallion at the Tuscany Exhibition for his two adding machines. Gonnella’s name is not to be found anywhere on this machine, just the inscription “I.P.C. Firenze“, which probably refers to the workshop that built the machine according to his design. It bears the number 59, which may refer to the year as this machine is so rare. Gonnella’s original thin book, which is today in the Arithmeum Library, was published in 1859. This machine is exactly as described therein.