10/31/2009. Remarks by W.T. Larkins: "Grumman experimentation with an amphibious Vought float for the O2U Corsair began in 1928 in an effort to duplicate the land-watercarrier performance of the OL-8. This early device was limited to a method of folding the wheels upward, which got them out of the way for water landings but left them exposed to cause excessive drag.
The first product of the new Grumman Aircraft Engineering Corporation was the development of a fully enclosed retractable gear amphibious float. The original model "A" float is shown above on the test O2U-4. This model of float was built in 1930 and Fleet tested aboard the Lexington and Tennessee in 1931. Note the step-down in the top of the wide float to allow propeller clearance.
At the same time Chance-Vought and Brewster were also building an amphibious float, but a thinner, revised flat-topped Grumman "B" float was given the production order that equipped VO-3B and VO-4B O3U-1's for Fleet service. Brewster continued their production of stainless steel non-amphibious floats and wing pontoons."