The Keystone XOK was an American biplane observation floatplane developed for the United States Navy during the early 1930s.
In 1929, the Navy issued requirements calling for an observation floatplane intended for service aboard Omaha class light cruisers, readily convertible to wheels or floats and light enough to operate from the cruiser-type catapult.
The Keystone design was a conventional biplane of mixed metal and fabric construction, with the pilot and observer seated in tandem in open cockpits.
[1] On April 15, 1931, during a demonstration before naval officials, the XOK-1 broke up in flight after the cowling detached itself and smashed into the wings and tailplane.
[1] With the Berliner-Joyce and Vought prototypes nearly ready for trials, the Bureau of Aeronautics elected to discontinue further development of the XOK-1.