The prototype 3244 observation was built by Budd in 1938 for El Capitan/Kansas Citian-Chicagoan/Golden Gate/San Diegan service..
The 3533 baggage by Budd in 1953 for general service.
The 505 by Pullman Standard in 1950 for Super Chief/El Capitan/Kansas City Chief service.
The cars as modeled by MTH actually don't have a prototype as such, but are based on the streamliners offered in HO by Athearn over the decades. They have a combination of mostly Budd and some Pullman Standard characteristics.
Rusty