This was a real chance sighting.
Earlier today was driving home and was close to the old B&O station in Old Town Gaithersburg, MD. I knew the Capitol Limited would be passing soon coming from Washington Union Station to Chicago so I pulled into the lot next to the station so I could watch it go by. The Cap came through on time (about 4:40) and - surprise - at the rear were three (I think three) passenger cars marked California Zephyr. Went by so quickly I only caught one name, Silver Solarium.
A cool little sighting on what was obviously a special excursion train with these interesting cars.