I have the same "set". If my recollection is correct, these came out over multiple years. The three coaches were released first - these were K-Line's first set of heavyweights (along with a couple of other road names). A year or two later the second 3 cars came out - these were the: observation, diner, and baggage. Then as the heavyweight line grew over the years the Pullman sleeper and RPO were added (note the different numbering systems with the K80- prefix). Later when K-line started doing interiors instead of the window silhouettes, they did a second PRR set of 6 cars (only one coach in the second set).
One warning on the early heavyweights - I also seem to remember there was and issue with the trucks that in a derailment they could get hot and even catch fire. There was a recall and fix, but obviously K-Line no longer exists, so there is no way to fix this now unless the trucks are replaced with another manufactures. Or, I guess just don't have any derailments.
