Depends on the era. "Round" end observations were introduced on the Broadway Ltd, Spirit of St. Louis, Trail Blazer and Liberty Limited in 1938 (+ or -). In 1948 - 1952, these were replaced with flat or squared ended observations. That also included the Congressional / Senator on the NE Corridor. By 1958, the use of observations began to fade, although they were still around and pulled by GG1s in the Amtrak Era. Dome Cars, OTOH, were never pulled by GG1s. They were not seen under the wire until the Conrail Office Car Train, which had an ATSF Full Length Dome / Dormitory Bar car on it, painted Pullman green. That was in the 1990s, behind diesels.