A.A. Porokhovshchikov was a Russian engineer who developed several military vehicle projects, and proposed them to the Russian Imperial Army during the WWI, and after 1917 - to the Red Army. Besides his more famous works, such as Vezdekhod light tracked vehicle and P-IV biplane, he came up with less successful ideas, such as composite vehicle armor. The initial idea behind this project remains unknown, but it was likely caused by shortages of armor steel plates. Another reason was the relative simplicity of metalwork done on boiler plates in small workshops. The composite plate consisted of 3 layers: 4.5 mm of heat treated boiler steel, a layer of dried and pressed seagrass, and another 3.5 mm boiler steel plate. The seagrass layer was also treated with an undisclosed compound, to increase its elasticity and viscosity. The reason behind such composition also remains unknown, the seagrass layer might had been added as a sort of anti spall liner, or shock absorber to prevent vibrations and friction between two metal layers. Later tests replaced it with a felt, which had no impact on armor's efficiency. Similar composition will later be applied on NI-1 armored tractors and JSP "sandwich" armored cars, though in these cases, the middle layes was made of wood.
Ford Model T 4x2 chassis was unchanged compared to the base model. Running tests weren't performed, although Porokhovshchikov claimed that excessive hull mass had no impact on reliability. The vehicle was manned by the crew of 4, armament consisted of a single 7.62 mm Maxim machine gun. Crew compartment had no doors or hatches, embarking and disembarking was performed through the open top. A protective brace was mounted at the front, intended for crossing barbed wire lines.
During the tests, it was shot at with Mauser 98, Steyr Mannlicher M1895, Nagant revolver and undisclosed Browning pistol. Firing tests demonstrated no penetrations from the firing distance of 35 meters. Regardless, the prototype composite hull was rejected due to its excessive mass compared to homogenous armor plates of comparable thickness.
Photos and information taken from A.G. Solyankin "Отечественные Бронированные Машины ХХ век", Chapter 1: 1905-1945. (Source), and M. Kolomiets "Броня Русской армии.
Бронеавтомобили и бронепоезда в Первой Мировой войне"
This device was developed in 1957 by Chelyabinsk Tractor Plant, Krasnoye Sormovo factory, and Oka shipyard. It was developed and tested in 1957, an improved version was indended to be developed throughout 1959-1961 to fit the upgraded T-10M. The system itself consisted of two pontoon units, with 6 styrofoam filled pontoons in total. A pair of pontoons was supposed to be mounted on each side, and smaller pontoons installed at the each end of the hull. As you can see in the first photo, side pontoons could be stacked on top of one another in the stowed position. Other components included engine snorkels and auxiliary fuel tanks mounted on the rear pontoon. The total weight was 14.635 metric tons. Assembly required 3-ton truck crane, and was supposed to be performed by 6-8 man crew within 1.5-2 hours. Upon landing, pontoons could be automatically dismounted by the driver.
The assembled device used integrated propeller driven propulsion system, powered from the tank's sprocket through the reduction gear unit. Top speed afloat was 11.5 kph.
The pontoons also had an extra stowage space, capable of taking up to 3 metric tons of payload. It is not entirely clear whether the device was supposed to carry landing assault troops, but considering the fact that PST-U, similar floatation device for T-54 tank, was suitable for this role, it shouldn't be ruled out. This idea is further supported by handrails and life preservers mounted on Object 755.
Photos and information taken from A.G. Solyankin "Отечественные Бронированные Машины ХХ век", Chapter 3: 1945-1965.