Chiesa is certainly a surname (example Damiano Chiesa patriot, Federico Chiesa footballer etc), Castelnuovo could be both a surname (example Nino Castelnuovo actor or also a locality Castelnuovo ne Monti or Castelnuovo Garfagnana or Castelnuovo Rangone in the Emilia Romagna region) while San Pietro Novello it is certainly a place in the province of Florence or Treviso. However, it was common practice, especially in light tanks, to write on the side the names of the commander or the place of origin of the crew or even pure nicknames of the vehicle such as "Garibaldino" or "Monarchico" or mottos of the Duce such as "Vincere" etc.... examples of that type can be found in the contemporary films "Luce"
All the best
Maurizio