The thesis aims to analyse a case of application of lean methodologies in a medium-sized Italian company operating in the goldsmith industry. In particular, lean methodologies are described from the literature and the jewelry industry sector is examined from an economic, strategic and industrial perspective. After that, the company's process of creating a line of jewelry in its prototyping and production phases is described in detail. Finally, the company's application of lean methodologies is studied with the aim of increasing the number of compliant products and thus improving the general quality level of production.