I would imagine he is juggling with grammes (very small ozs,)

I cant find the weight of the original but I suspect the total weight of the model boat is about 0.5 kgs 18 ozs.
Did find a bit of history of MAS 568 !
The night between 2nd and 3rd August, Mas 573 (capitano di corvetta Castagnacci), 568 (sottotenente Legnani) and 569 (sottotenente Ferrari) attacked, southwest from Kerch, heavy cruiser Molotov ("Kirov" class) (2) and naval destroyer Kharkov ("Leningrad" class ), which were on intercept German transports mission. the two large Soviet units, commanded by Commodore N.E. Basisty went near the coast, opening fire, with their 181, 122 and 100 mm. guns, against objectives situated between Iwan Baba and Feodosia. Realizing the great danger (the attack of a powerful 11.500 tons cruiser, armed with nine 181 mm. guns, against a flotilla of German small barges, which were in that part of sea, certainly should have been ended in total disaster), Mas 573 and 568 commanders decided to immediately attack the large enemy unit. Torpedoes from Mas 573 missed, but Legnani's Mas 568 went at very short distance from the cruiser and launched its two torpedoes: the first missed, while the second succeeded in hitting the aft hull of Molotov cruiser, which, meanwhile, was hammering Italian units with its 100 and 45 mm. guns. After the strike, Mas 568 tried to losing touch with the adversary with a quick evasive maneuver, but was chased at full speed by destroyer Kharkov, which meanwhile was arrived to help the Molotov. With a remarkable cold blood, commander Legnani ordered his men to drop from rear all the ten little depth charges the unit had aboard, triggering them on the minimal explosion depth. Depth charges exploded in a fast succession, quite ahead of Kharkov prow, damaging it so badly to force the Russian destroyer to stop the chase. Either Molotov and Kharkov retired from the combat toward east to reach as soon as possible their base. Mas 568, which within only 15 minutes succeeded in damaging the two enemy units, could return to Yalta, also if damaged and attacked by some Soviet aircraft, drawn by explosion's lights.
Reproduced from
http://www.icsm.it/regiamarina/blacksea.htm