daylight disk at 200 meters

Sighting - Late June 1967   When I was 13, I was standing on the front porch of our house in the early afternoon with my sister ((name deleted)), who was looking off the other way while I gazed across the cornfield to the north.  
Suddenly an object came over the treeline along the right edge of the field at about 200 meters from me and 100 feet off the ground.
It was a bright shiny silver disk about 50 feet in diameter making no sound other than that of it splitting the air.  I distinctly remember seeing a slight vapor coming off the edges of it as it moved through the air at perhaps 350 mph.
It passed out of my sight over the woodlot  at the left side of the field quickly, but I had seen it and gotten a very good look at it.  I didn’t tell anyone about it for more than 30 years.  I wish I had, but then I was the only one who saw it and at that age did not expect to be believed.
We need to report these things, people.
Witness does not indication location of sighting.  Date above is approximate.  PD