Acciaio-class submarine

The Italian  Acciaio class submarine (also sometimes called Platino class ) was the fifth subclass of the 600 Series of coastal submarines built by the Regia Marina. They were completed during the early 1940s and saw service in World War II. The Acciaio's were a development of the Adua and Perla designs, with some improvements, such as a lower conning tower to improve stability and reduce the silhouette. Of the 13 vessels in the class, six were built by CRDA at Monfalcone, four by OTO at Muggiano, and three by Tosi in Taranto, the three main Italian shipyards for submarines. They were single-hulled with side tanks, and built to a Bernardis design, though the Tosi vessels had more powerful engines (at the expense of the two stern torpedo tubes, giving a surface speed of 14.7 knots. The word Acciaio means "Steel", and all vessels in this class were named for metals and minerals.

Of the 13 vessels completed 8 were lost in action, serving in the Mediterranean theatre of operations.