Black round obj with seq flashing green lights, 6-8 in wide viewed at arm's length, and seen in daylight -- and no wings!

I know this is an old sighting, but I've never reported it before and have to get it off my chest!  ... I was driving south on Rt. 70S (now Rt. 270) and had just gone under the Shady Grove Road overpass.  The day was gloomy, almost like a foggy-rainy day but it was not raining; the clouds just seemed to be very low.  As I came out from the underpass, I saw this "big thing" above me.  It had no wings that I could determine and I tried hard to speed up to keep getting a better look.  I probably got up to about 80, but it was no contest.  It was black (I could only see the underside at first), and at arm's length I would say it was about 6-8 inches in diameter, a real big-un as they say. As it continued south in front of me and drew away, I could see that it had green sequentially flashing lights along the rear (but I could not, of course, see whether these lights went all around the object).  It then slowly changed course toward the East and I lost sight of it because I had to drive.  I think the object was going about 300-400 mph -- it reminded me of the way a C130 had looked the day a friend said, "It isn't going that slow, it is just that big."  I let it go out of my mind, but the next morning I heard on the radio that the Air Force had reported that the object seen by a number of people was an experimental plane they were testing.  It did seem to me that something that size would have had a budget that people would be arguing about.  If it was a secret, why were they testing it in broad daylight?  And, most of all, why didn't it have any wings?  I would love to hear from anyone else who has seen something similar.