It is necessary to put this watch in its context. At the end of World War II, the demand for Swiss watches exploded, but it was mainly for economical watches. Chronograph manufacturers understood this and adapted: if the Chronodato from Angelus or the Tricompax from Universal were successful, it was because they were also affordable.
In addition, the largest supplier of calibers, Ebauches SA, initiated the development and production of economic chronograph calibers at the end of the 1930s, in particular with the development of the calibers without column wheel Landeron 47 and 48 [1] (1939-1940), and the economic caliber Valjoux 77 ECO (1946).
Minerva (in fact Minerva Sport) being a Manufacture did not have access to the calibers of Ebauches SA [2]. André Frey and Maurice Favre, who directed the company at that time, thus took the decision to design their own economic caliber.
The patent [3] was filed in October 1944 but not published until January 1948. It concerns a chronograph with a simplified mechanism, without a column wheel, with a vertical clutch that saves wheels, more economical wire springs, and even a coil spring for the hammer return, typical of sports counters. This is a far cry from the beautiful polished and beveled parts of the beautiful Minerva 13-20! The coil spring was well known at Minerva: its application in sport counters had been patented as early as 1930.