Start with what the Maserati 420 is: a car with gasoline engine, from Maserati. What it meant takes a little longer.
What is underneath
The engine is gasoline engine. On the scales it comes to 1187 kg. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
Its place in the line
Nearby in the Maserati catalogue sit the Maserati 150S and the Maserati 200S.