These cars were originally sold by MDC/Roundhouse, and later on by Athearn. The Roundhouse cars were available both as a kit and RTR. For the most part, these are sold in four car sets (sleeper, combine, coach and business). However, add-on coaches are also available as singles. Although the exact prototypes for these models is unknown, they are representative of the typical sorts of passenger cars in common use in the late 1800's.
Four car set -