Giuseppe Guadagnini I was trained by his father, Giovanni Battista, and had assisted him during his the 1760s and 1770s in Parma and Turin. By the settling of the family workshop in Turin in 1771, he was already a crucial contributor to his father’s output, together with his elder brother, Gaetano.
After the end of the collaboration between G.B and the Cozio of Salabue in 1777, Giuseppe left Turin for a period of over 20 years in which he worked independently from his father, developing his very own personal style and approach, with some shared aspects. Giuseppe's subsequent place remain somewhat of a mystery. In the world of violin connoisseurs, he's often referred to as 'Il Soldato,' a nickname stemming from a tale suggesting he may have served in the military, though concrete evidence supporting this claim remains elusive.
As far as we can understand, the relationship between Count Cozio and G.B Guadagnini is directly linked to that with the other members of the Guadagnini Family. If we consider that 'Il Soldato' worked under his father at least until the age of 25, he spent the greater years of the collaboration between the young aristocrat and his father with hands on the bench answering to Count Cozio's requests. Through the Turin period, especially between 1771 and 1780 (Which includes the exclusivity contract with the Count), Guadagnini's workshop produced an average total of 20 Instruments per year, making the participation of his sons in the making process undeniable.
In the next decade, there are two main reasons that explain the considerable reduction in the production rate of Guadagnini's workshop: The reduction of Count Cozio's demand since the end of the exclusivity contract in 1777 and the absence of Giuseppe in the workshop. 'Il Soldato left his father's workshop circa. 1778, leaving the business control gradually in the hands of his brother Gaetano, along with the other members of the family who were tendentially more interested in making and trading picked string instruments.
Giuseppe Guadagnini was only a couple of years older than the Count, and it is unlikely that they didn't collaborate later after G.B. Guadagnini's death, with Cozio being such an important client. Duane Rosengard mentions in his book that one of the instruments kept in Cozio's collection was a Mandolin made by Giuseppe Guadagnini, and since picked strings instrument could be considered a marginal interest of the Count, it should show a certain level of admiration from Cozio to 'Il Soldato'.