The Namur, Belgium picture set taken by the "Belgian repairman". The photos were taken on June 5, 1955 around 7:30pm. UFO researcher, Aime Michel wrote up the original case and kept the witness anonymous.
The witness stated that he saw the object arrive swiftly in the area and then slow to a hover. The witness who travelled with a camera got it focussed and took one shot. "The witness indicated that he has visually seen a sharp gleam moving high in the sky without any noise and at high speed. He indicated that the gleam accompanied an object of discoïdal shape leaving a white trail behind him."
It "posed" briefly, looking silvery gray and brightly shining. Beneath the disk where four legs as if landing supports. The craft then dove slowly, leaving a vapor trail, and he took a second shot. "The witness continued by indicating that the object lost altitude, made a turn and then went upwards to reach his own trail."
Michel got a meteorologist to examine the originals, and he thought that the trail was due to genuine atmospheric condensation. Given the weather conditions, the expert suggested that the disk had to be at least at an altitude of 1500 meters to produce a trail. If so, the minimum diameter of the disk was 12 meters(40 feet).
Finally the object rose up and passed through its own trail, and the witness managed to get his third shot. "The witness continues by explaining that when the object joined its trail, the trail was dissipating, the UFO then accelerated and left, while luminous particles were ejected behind it."
Aime Michel original Article: Three Genuine Photographs; Why They Are Authentic