A memorandum says that on 1 July 1947 a GCA operator at Chitose AAB observed a target traveling at more than 600 mph and making four turns on the scope.
“On 1 July 1947 a GCA operator at Chitose AAB, Hokkaido,
reported that a target travelling at a speed in excess of 600 mph
was observed and further that the target made four turns on the
scope.”
Source: "A-1: Completely reliable" radar sighting of unidentified aircraft
// Chunk 2; source chars 22295-32864; chunk 2 chars 22295-32864; 8 August 1947 memorandum