Macchi M.C.99

The Macchi M.C.99 was an Italian torpedo-bomber flying-boat prototype of the 1930s that was designed by Mario Castaldi and produced by Macchi.
It was a military flying boat that was heavily based on the previous civilian flying-boat airliner Macchi M.C.94 and, just like that one, it was a wooden twin engined shoulder wing-cantilever monoplane made almost entirely out of wood.
It had a crew of five, two pilots, and three gunners/observers. An enclosed cockpit and three defensive posts in the bow, amidships and the tail, with two 7,7mm Breda-SAFAT machine guns mounted inside a turret in the bow with the machine guns placed one above the other. It had another turret in the amidship with another 7,7mm Breda-SAFAT and another one in the tail under the vertical stabilizer. It was powered by two 1190hp Isotta-Fraschini engines mounted in struts above the wings.
There was only one airplane made in 1937 and it served with the 170º Squadriglia (170th flight) of the Aviazione Ausiliaria per la Marina (Navy's Auxiliary Aviation), under direct command of the Navy's Command for Sicily, until the airplane was dismantled in Augusta, Sicily.

Sources:
1. https://en.wikipedia.org/wiki/Macchi_M.C.99
2. https://it.wikipedia.org/wiki/Macchi_M.C.99 (translated)