A maker of clocks and scientific instruments, Girolamo continued the business of his father Camillo (1484-1560) and his uncles Benvenuto (1486-1532) and Eufrosino (late 15th C. - 16th C.). In 1554, he made an armillary sphere, now preserved in the Science Museum in London. In 1560, he succeeded his father as superintendent of the large clock in the Palazzo Vecchio. He also asked to be assigned the maintenance of his grandfather Lorenzo's (1446-1512) Orologio dei Pianeti [Planetary Clock], which he restored himself. In 1564, he designed a clock for the Piazza San Marco in Venice. In 1590, he built his last clock, preserved at the Museo Galileo of Florence (inv. 2460).