I have nothing in my files on this. UFOE lists Keyhoe [FS Conspiracy] as its source, but Keyhoe's brief mention is garbled. The "best" statement of the case comes from the always risky Frank Edwards [FS: Here & Now]. Here he claims to have been the main contact for the source. Hopefully there are more official sources in the BB files.
Source: Flying Saucers: Here & Now, page 84
May 13, 1954
My information on this first case comes from the electronics specialists who were involved. I was based in Washington at the time, and several of the parties \vho reported to me were personal friends of mine.
On that day, shortly before noon, a team of experts were putting the finishing touches on a new type of radar. They noticed that it was recording some type of object at oreat altitude something of unusual size. They double-checked by switching on another unit, and it too began tracking the same object. They were able to determine that it was at least two hundred fifty feet in diameter, about fifteen miles above Washington, and that it was moving from point to point around a rectangular pattern in the sky at about two hundred miles per hour. After three hours of this maneuvering, under the scrutiny of several government radar installations, the object finally moved toward the west and disappeared from the screens.