photo was sent to the American monthly Popular Science showing the number twenty-three. British Power Boat 72 ft MTB Initially ordered as an MGB in 1941; they were converted to MTBs (412-418, 430-432, and 534-500) from 1942 by addition of two 18-inch tubes and a 6-pdr gun. Although 10 tons heavier after conversion they still made 39 knots. Vosper 45 ft MTB Built as a private venture, the 45-ft MTBs were scaled down versions of larger Vosper design and intended to be carried by larger vessels. As MTB 104 to 107, these were taken up by Admiralty but found to be poor seakeeping and not used for combat. Vosper 70 ft MTB Although various boat lengths were produced by Vosper for the Royal Navy, the "70 ft" boat was produced from 1940. The design was produced with modifications as MTBs 31-40, 57-66, 73-98, 222-245, 347-362, 380-395 and 523-537. Using three Packard V1-12 marine engines, they were capable of around . Early models carried two torpedo tubes, twin machine guns in a "bin" behind the bridge and two machine guns. They could also carry four depth charges. The Vosper 70 was also used in other navies, such as Romania's, which acquired three in 1939, with NMS Viscolul the lead ship of the class. Vosper 73 ft (Type I and Type II) Between 1943 and 1945, the "Vosper 73ft" design appeared, the type II differed in that it carried a heavier gun armament at the expense of two torpedo tubes. The Type II did not enter service before the end of the war but was in use after the war. Type I Length: 73 ft (22 m) Engine: 3 Packard 4M V12 engines for a total of 4,200 hp Speed: Range: at Displacement: 47 t Armament: Four torpedo tubes Oerlikon 20 mm cannon Two 0.303 in Vickers K machine guns (optionally two Vickers .50 machine guns) Crew: 13 Type II Length 73 ft (22 m) Engine 4,200 hp Speed Range at Displacement 49 t Armament Two torpedoes 57mm QF 6-pdr Mark IIA gun on powered mounting Twin 20mm Oerlikon aft Two 0.303 Lewis Guns Crew 13 Thornycroft 75 ft MTB The first two (MTB 24, 25) were actually 74 ft prototypes for the design ordered in 1938. Powered by three Isotti-Franschini engines they could reach 37 knots. The later ones, MTBs 49-56, had four Thornycroft RY12 engines but were too slow for