The early Ca.313s could also be distinguished by their noses. The early model Ca.313 - eg: the Swedish Ca.313S (Svezia, aka Ca 313RPB/S to Caproni), Ca.313F (Francia) for the AdA, and Ca.313 RPB.1 for the Regia Aeronautica had fully-glazed noses. By contrast, the later Ca.313 RPB.2 for the Regia Aeronautica had the short, stepped nose of the Ca.314.
BTW: RPB = Ricognizione/Pattugliamento/Bombardamento