Shaped somewhat like a bus, army green in color, no wings, no engines, completely silent, no ID markings, had windows but no lights on

In the early 1960’s my brother and I were outside playing some football in our backyard. It was in the Fall and later in the afternoon. The sky was clear. As we were playing we noted “something” coming from the northeast moving to the southwest. It looked “bus” like except the front had more taper than the rear. It was army green in color, had windows (but no lights could be seen). The object was flying about 500 feet off the ground. We did not see any wings or engines of any type. The object flew without a sound. Its flying speed was slow so we had at least 5 minutes to observe it. There were no markings or identification of any sort on the object. I sure wish I had a camera available that day. Since that time my brother has passed on so I am the only observer. I remember seeing it vividly after all these years the experience was that impressive.