Just saw an Amtrak regional with a dome car on the tail end. I was a little surprised and didn't get a detailed look, but it said something like North Pacific and Vista Dome on it. It was southbound at about 1:10 pm about 6 miles north of the Staples Mill station in Richmond.
Was this the car you saw?
http://www.aaprco.com/cgi/cars/cardispl ... -dome:type