Given the thread topic, most of the discussion so far has concerned the leading car of the pair, Advance, later Bear Flag as the first duplex room car, it has occurred to me that the other car, Progress later California Republic, was the first of the parabolic curved streamlined observations that became so well known on trains across the USA (except of course for the articulated Zephyrs).
If anyone can think of an earlier separate car that had such an observation, I'd like to hear about it. The Milwaukee Hiawathas had observation cars but quite different in design and appearance.
The Broadway, 20th Century, the Lark and all the other trains that had this style were all later. Even Pullman's own American Milemaster was much later.
Peter