A Brief History of the Marque
A company in Pessano con Bornago, Milan, specializing in the production of motocross and enduro machines including the 50cc Minicross in three versions, Junior, Senior and Professional, and RX/MX80 for cross and enduro.
In the address of Tresoldi srl for 2016 is listed as:
Strada Provinciale, 64, 20060 Pessano con Bornago MI, Italy
Apparently they have a small museum with a history of the marque.
Sources: MC Storico Conti et al